The Equine Nervous System: Part 2 - Diving Deeper

Diving Deeper into the Horse’s Neuroanatomy and Behavior

In Part 1 of our nervous system overview, we explored how the brain, spinal cord, and peripheral nerves work together to help horses sense, move, and survive. In this second installment, we take that understanding further by examining the complex inner workings of the equine nervous system. You'll discover how this system influences movement, emotion, coordination, and neurological disorders—and how to recognize when something goes wrong.

Make sure you have read our article "The Equine Nervous System" before you read this one.

TL;DR

• CNS vs PNS vs Autonomic: Part 2 goes beyond anatomy. You’ll learn to localize problems (cervum/cerebellum/brainstem vs limb plexuses) and read autonomic state (fight/flight vs rest/digest) so training and triage are smarter.

• Field patterns that matter: Worse on tight circles/backing = neurologic until proven otherwise. Asymmetric = think EPM; symmetric in youngsters = think EDM/EDX; forelimb + hind = consider cervical cord; head tilt/poor blink/swallow issues = brainstem/cranial nerves.

• Quick owner screen: Film straight line → small circles both ways → backing + a face close-up (menace/blink/tongue tone). Compare to your horse’s normal vital signs and average heart rate.

• Autonomic “down-shift”: After work, HR/RR should trend toward baseline within minutes; the eye softens and gut sounds return. If recovery stalls—or there’s no sweat in heat—scale back, cool, and call your vet.

• When to call now: Trouble swallowing, head tilt/poor blink, urine dribble + weak tail, fever with sudden hind ataxia (isolate—suspect EHV-1), or no recovery by 10–15 min after moderate work.

  
  

The Central Nervous System: More Than Just the Brain

The central nervous system (CNS)—brain + spinal cord—does far more than “think.” It filters sensation, chooses responses, times movement, and runs life-support reflexes. When it falters, you don’t just see a sore limb—you see coordination changes, cranial-nerve clues, or altered mentation.

What “central” means

The CNS integrates incoming senses (eyes, ears, skin, joints) with stored patterns (habits, training) and automatic control (swallowing, breathing, heart rate). That’s why a horse can spook, down-shift, and then step cleanly over a pole within seconds—the brain and cord are coordinating the sequence.

Horse's brain. Credit: Veterinary Anatomy World

Cerebrum — perception, decisions, habits

What it does

Interprets sights/sounds/touch, starts voluntary movement, and encodes associations (“one cue → one meaning”).

How it shows up in work

Repetition smooths patterns; scary-but-safe things fade into background with controlled exposure.

Red flags

Sudden behavior change without clear context (no tack, footing, or environment cause). New anxiety or dullness vs the horse’s normal.

Cerebellum — timing, balance, smoothness

What it does

Scales rate, range, and rhythm so each joint moves the right amount at the right time.

How it shows up in work

Clean poles/transitions; confident foot placement on hills or uneven footing.

Red flags

Overshooting/stabbing steps, pole knock-downs during easy tasks, feet that wander on small circles.

Brainstem — life-support hub

What it does

Runs autonomic functions (swallowing, breathing, heart rate) and relays signals between brain and cord.

Owner-critical signs (urgent)

Trouble swallowing, abnormal breathing, profound lethargy, or multiple cranial-nerve deficits (e.g., facial droop + poor blink).→ Stop work, record short video, check vital signs and average heart rate, and call your veterinarian.

Spinal cord — segmented superhighway

Organization you can see

• Cervical (neck) → forelimbs & part of trunk

• Thoracic/Lumbar → trunk + hind-limb coordination

• Sacral → tail tone, pelvic/perineal function

Field patterns (owner lens)

• Cervical: toe-drag/stumble in front, worse on tight circles/backing.

• Thoracic/Lumbar: hind swings wide; backing goes crooked.

• Sacral: flaccid tail, urine/fecal control changes.

Reflexes — local vs central

Spinal reflexes (withdrawal, patellar) can fire without conscious brain input—useful for triage.

Cranial-nerve reflexes (menace, palpebral blink, tongue tone) screen brainstem functions. Abnormal ≠ diagnosis, but they’re valuable clues for your vet.

Mini-scenarios (quick localization)

• Trips in front on small circles → likely cervical cord pathways. Film straight/circles/backing; pause ridden work; vet.

• Starts knocking poles, “flappy” behind at easy effort → consider cerebellar coordination; switch to assessment.

• Drops feed + one ear/eyelid won’t move → brainstem/cranial nerves; protect the eye (if trained) and call the vet now.

CNS at a glance

CNS Region	What it Serves	Good Looks Like	Quick Red Flags	Your Next Step
Cerebrum	Perception, decisions, learned responses	Appropriate reactions, consistent cue meaning	Sudden behavior shift without cause	Video + vitals; vet if persistent
Cerebellum	Timing, balance, coordination	Smooth poles/turns; accurate feet	Exaggerated/under-scaled steps on easy tasks	Pause training; vet assessment
Brainstem	Swallow, breathe, heart rate; relay	Easy swallow, normal breathing, bright	Dysphagia, abnormal breathing, multi CN deficits	Urgent vet; check HR/RR
Spinal (Cervical)	Neck → forelimb pathways	Clean forelimb placing	Toe-drag/stumble front; worse on circles/backing	Stop riding; film; vet
Spinal (T/L)	Trunk & hind coordination	Straight backing; steady hind	Hind swings wide; crooked backing	Vet if consistent
Spinal (Sacral)	Tail tone, pelvic/perineal	Firm tail; normal elimination	Flaccid tail; urine/fecal issues	Prompt vet; protect skin

CNS red flags vs “training problems”

Does it get worse on tight circles or backing? That pattern fits neurologic ataxia, not laziness or stiffness.

Are swallowing, breathing, or facial movements off? That’s brainstem/cranial-nerve territory—medical, not training.

Did rest fix it? Mechanical lameness often eases with rest; neuro signs usually don’t.

Handling & safety while you wait for the vet

Use level footing and a quiet handler. Keep sessions short. Do not ride. Avoid lifting a hind high if there’s tremor/weakness. Protect the eye if the blink is weak (use lubricant only if you’ve been shown how). Log temp/HR/RR and capture video: straight line, small circles each way, and backing.

Owner takeaway

CNS problems rarely “school out.” If signs are inconsistent and worse on circles/backing, or involve swallow/breath/cranial-nerve changes, switch from training to assessment: video, vitals, call your vet.

Put this into practice with the Neuro Screen & Localization Assistant—log today’s video findings and compare to your horse’s baseline.

Peripheral Nervous System: The Body’s Messenger Network

The peripheral nervous system (PNS) is every nerve that leaves the brain and spinal cord to reach the body—and every sensory line that brings information back. If the CNS is the control tower, the PNS is the wiring harness: it carries signals for touch, pain, position, temperature, and movement.

What the PNS does

Sensory (afferent) nerves report what’s happening: where each hoof is, how tight the girth feels, whether a fly just landed on the flank.

Motor (efferent) nerves tell muscles and glands what to do: step, flex, swallow, sweat.

When PNS wiring falters, you see weakness, reduced sensation, or mis-timed movement—often in a specific region that matches the affected nerve or plexus.

Spinal nerves & plexuses

Each spinal segment gives off a pair of nerves. Bundles of these form plexuses that serve limbs and trunk.

Brachial plexus (forelimb focus)

Carries motor/sensory supply to the shoulder, arm, forearm, and foot.

Field clue: forelimb weakness, short stride, or stumbling after shoulder trauma or awkward pulls.

Lumbosacral plexus (hindlimb drive)

Feeds the gluteals, hamstrings, gaskin, and distal hind limb.

Field clue: weak push, scuffing toes behind, difficulty backing straight.

Small injuries (stretch/compression) can temporarily stun a plexus; larger injuries can cause marked weakness and muscle wasting.

Cranial nerves: head, face, special senses

Twelve cranial nerves exit the brain to run vision, balance, facial movement, chewing, and swallowing. Owner-useful checks are simple, fast, and not diagnostic on their own:

• Vision (CN II): obstacle avoidance; does the horse track a hand?

• Facial movement (CN VII): even blink and ear/lip motion?

• Balance (CN VIII): head tilt or drifting?

• Chew/swallow (CN V, IX, X, XII): drops feed, coughs water, tongue feels flaccid?

If any are abnormal, stop work and call your vet—protect the eye if blinking is poor.

Somatic vs autonomic (voluntary vs automatic)

Credit: veteriankey

The somatic system controls voluntary skeletal muscle. That’s your half-pass, your clean halt, your careful hoof placement over poles.

The autonomic system (ANS)—a branch of the PNS—runs heart rate, gut motility, sweating, and pupil size. It has sympathetic (“go”) and parasympathetic (“recover”) halves. You’ll see ANS shifts in vital signs and heart rate.

Quick owner table: PNS map you can use

PNS Region	What it Serves	Field Signs When Off	Easy Barn Check (not a diagnosis)	Next Step
Brachial plexus	Shoulder → forefoot	Forelimb weakness, short/guarded stride, tripping	Gentle tail pull stays normal; fore stays weak	Vet exam; rest; imaging if trauma
Lumbosacral plexus	Gluteals, hamstrings, hind distal limb	Weak push, toe scuffing, crooked backing	Back 4–6 steps; watch limb path	Vet exam; rule out spine/hoof pain
Cutaneous sensory nerves	Skin sensation	Over/under-reacts to touch, girthy without cause	Light touch mapping along trunk/limb	Check tack/skin first; vet if persistent
Cranial nerves	Vision, face, swallow, balance	Head tilt, facial droop, dropped feed	Menace/blink/tongue tone	Prompt vet; protect eye
Autonomic fibers	HR, gut, sweat	Anhidrosis or over-sweating; HR doesn’t settle	Compare to your horse’s usual HR/RR	Review vitals; vet if abnormal

PNS red flags vs training problems

Does the issue localize to one region?

Forelimb only, or hind only, points to PNS/segmental causes—especially after a fall, pull, or awkward cast in the stall.

Is sensation altered?

A horse that doesn’t react to a firm touch where it normally would—or overreacts to a light touch—may have a sensory nerve issue, not a manners problem.

Are head/face signs present?

Facial asymmetry, odd eye position, or dropped feed signal a cranial nerve problem. That’s medical, not training.

Handling & safety while you wait for the vet

Use level footing, a quiet handler, and short sessions. Avoid asking the horse to hold a hind foot high if weakness/tremor is present. Protect the eye if the blink is weak (lubricant only if you’ve been shown how). Log temp/HR/RR and a short video (straight line, circles, backing).

Owner takeaway

The PNS is regional and specific—your observations about which limb, which sense, and what changed help your veterinarian localize the problem quickly. When signs point to a nerve or plexus, stop training, gather good video, check vitals, and get a vet assessment.

Autonomic Nervous System: Balancing Survival and Serenity

The autonomic nervous system (ANS) runs your horse’s background settings—heart rate, breathing, gut sounds, sweating, pupil size. It has two halves that constantly trade control: sympathetic for mobilizing (“go now”) and parasympathetic for restoring (“rest and digest”).

A healthy horse cycles up for work and settles back down within minutes. Training sticks—and health holds—when that down-shift is reliable.

What “sympathetic” looks like in real life

When the sympathetic system takes the wheel, everything looks a little sharper and faster. Breathing picks up, heart rate climbs, muscles feel spring-loaded, and the eyes are wide and bright. In warm weather or under effort, sweat comes on quickly—unless the horse is anhidrotic, in which case the coat may stay worryingly dry even while the horse runs hot.

That surge is useful for short bursts of focus or escape, but it’s not a place to live. If the “on” state lingers—minutes after the stimulus is gone—you’ll see learning quality drop, coordination get sloppy, and heat or gut risks creep up. That’s your cue to scale the work down and guide the horse back toward recovery rather than pushing through tension.

What “parasympathetic” looks like

As parasympathetic tone returns, you can watch the body let go. Breathing slows, the heart rate eases toward that horse’s normal, and the face softens around the eyes and lips. Gut sounds resume in steady gurgles along both flanks, and small signs of comfort—licking, chewing, a quiet sigh, a head-lower—start to stack up.

Chewing hay in the sun is the everyday picture of this state, and it’s the place you want to finish training. Ending sessions here teaches the nervous system what “done and safe” feels like, so tomorrow’s work starts calmer, learns faster, and recovers more cleanly.

Keep a baseline for comparison:The Horse’s Vital Signs and Average Heart Rate.

Quick table: organ-by-organ effects you can observe

System/Sign	Sympathetic (Go)	Parasympathetic (Recover)	What you can check
Heart rate	↑ HR for effort/stress	Baseline HR returns	Take HR pre-ride, 2, 5, 10 min post (see Average HR)
Respiration	Quick, shallow	Slow, regular	Count breaths; watch nostrils & flank
Gut motility	↓ (quiet gut)	Normal/active borborygmi	Listen both flanks 60 sec
Sweating	↑ (or none if anhidrosis)	Normal/none at rest	In heat: uniform sweat vs dry patches
Pupils/eyelids	Dilated, tight	Normal, soft	Eye “feel” + facial tension
Behavior	Startle, scanning, pacing	Focus, head low, exhale	“Startle → settle” time

Not sure if it’s central or peripheral? The Neuro Screen & Localization Assistant highlights patterns and flags biosecurity risks.

Health & management through the ANS lens

Heat and sweat

In warm weather a working horse should sweat evenly as the sympathetic system ramps up and the body sheds heat. If the coat stays oddly dry, or only small patches sweat while the horse still looks hot, think anhidrosis rather than fitness. Move to shade, hose and rinse–scrape in cycles so water actually pulls heat off the skin, and offer cool, palatable water. If recovery is sluggish or the pattern repeats on routine rides, that warrants a veterinary plan—don’t “work through it.”

Gut sounds and stress

Short-term quiet gut sounds are normal during arousal; prolonged silence is not. After work or a stressful moment, you should hear a steady return of gurgles on both flanks as parasympathetic tone comes back online. Help that recovery with simple management: consistent turnout, continuous forage, and a predictable schedule. If gut sounds stay quiet alongside an elevated heart or respiratory rate, call your veterinarian rather than waiting it out.

A simple de-escalation routine (in hand or mounted)

When you feel tension rise, make space for a reset. Breathe out slowly and let your aids soften with the exhale; your horse will often mirror you. Ask for one easy behavior your horse knows cold—halt-park on a loose rein or a large, relaxed circle—then watch for the first sign of settling: a sigh, a head-lower, a soft blink. Name that moment (“easy”), give thirty seconds of true rest, and carry on. Ending a session on that calm state teaches the nervous system what to return to next time.

When the ANS says “call the vet”

Most training hiccups settle as the parasympathetic system comes back online—breathing slows, heart rate drops, gut sounds return, the eye softens. When that recovery doesn’t happen, or when certain signs appear, you’re no longer in “training” territory—you’re in medical territory.

Call your veterinarian now if you see any of the following:

• Trouble swallowing (dropped feed, coughing water) or repeated choke-like episodes.

• No sweat in heat, or collapse/exhaustion signs despite cooling.

• Persistent quiet gut with stress or after work (silence that lasts, not minutes).

• Urination problems (dribbling, straining) or a flaccid tail/weak anal tone.

• Facial asymmetry or a poor blink (eye can’t close)—protect the eye while you wait.

• Resting heart rate or breathing rate that stays well above your horse’s normal without an obvious cause.

• Failure to recover toward baseline within 10–15 minutes after moderate work—heart rate, respirations, and demeanor all remain “wired.”

If fever (or a recent fever) appears with sudden hind-end incoordination, weak tail tone, or urine dribbling, isolate the horse immediately and call your vet—manage as a potential EHV-1 situation until told otherwise.

While you wait, stop all ridden work, move to shade or a quiet stall, start cooling and hydration as appropriate, and jot down objective numbers. Compare against your horse’s own baseline using The Horse’s Vital Signs and Average Heart Rate. Short videos (straight line, small circles, backing, and a close-up of the eyes/face) help your veterinarian triage faster.

Self Assessment Quiz: Equine Nervous System

Multiple Choice

1) Which real-world signs best indicate a sympathetic surge?

• a) Slow breathing, soft eye, steady gut sounds

• b) Faster breathing and heart rate, tight muscles, bright wide eyes

• c) Head low, licking/chewing, drowsy posture

• d) Audible gurgles on both flanks

2) After moderate work, what best reflects a healthy return to recovery?

• a) HR/RR continue to climb; tense jaw; scanning

• b) HR/RR trend toward baseline; sigh/head-lower; gut sounds return

• c) Patchy/no sweat in heat; pawing; restless pacing

• d) Silence of gut sounds for hours

3) In warm, humid conditions the coat stays dry despite effort and the horse runs hot. Best interpretation?

• a) Excellent fitness; increase workload

• b) Normal rest-and-digest state

• c) Possible anhidrosis; stop, cool, hydrate, consult your veterinarian

• d) Simple dehydration that will self-resolve

4) Which plexus primarily innervates the hind limbs?

• a) Cervical plexus

• b) Thoracic plexus

• c) Brachial plexus

• d) Lumbosacral plexus

5) Which finding points most strongly to a cranial-nerve problem?

• a) Toe drag in the hind limbs on small circles

• b) Facial asymmetry with a poor blink and dropped feed

• c) Stiffness on the first trot circle that warms out

• d) Shorter stride only on hard surface

6) Sensory (afferent) vs motor (efferent) nerves are best described as:

• a) Sensory send commands to muscles; motor carry touch and pain

• b) Sensory bring information in; motor send commands out

• c) Both carry only pain signals

• d) Both are cranial nerves only

7) Which pattern most suggests a cervical spinal cord pathway issue?

• a) Toe drag in front, worse on tight circles and backing

• b) Unilateral facial paralysis and head tilt

• c) Hind-only weakness that improves with rest

• d) Pain on palpation over the sacrum only

8) The cerebellum’s primary role is to manage:

• a) Sensory interpretation and memory storage

• b) Balance, timing, and coordination of movement

• c) Autonomic control of heart rate and breathing

• d) Hormone release from the pituitary

9) The brainstem is most closely associated with:

• a) Voluntary planning and habit formation

• b) Fine motor timing and error correction

• c) Swallowing, breathing, heart-rate control, and cranial-nerve reflexes

• d) Skin sensation and sweat distribution

10) Which observation best fits a regional peripheral nerve/plexus problem rather than a global central issue?

• a) All four limbs inconsistently place worse on backing

• b) Sudden hind-only weakness after a fall, with normal mentation and cranial-nerve checks

• c) Head tilt and uneven blink with swallowing difficulty

• d) Symmetric ataxia in a youngster with normal muscle mass

11) Which finding best fits an upper motor neuron (UMN) pattern?

• a) Marked atrophy with reduced reflexes

• b) Long, weak stride with delayed placing, worse on circles/backing

• c) Normal placing but cannot push

• d) Focal denervation of one muscle group

12) You observe fever yesterday, sudden hind ataxia today, and urine dribbling. First barn action?

• a) Hand-walk to relax

• b) Give NSAIDs and ride lightly

• c) Isolate the horse and call your veterinarian (suspect EHV-1)

• d) Longe to assess symmetry

Answer Key

1. b

2. b

3. c

4. d

5. b

6. b

7. a

8. b

9. c

10. b

11. b

12. c

Frequently Asked Questions (FAQ)

1) What are the quickest red flags that a problem is neurologic, not training?

Incoordination that’s worse on small circles or backing, sudden toe-drag, head tilt/uneven blink, trouble swallowing, or weak tail/urine dribble. Stop riding, record short videos (straight/circles/backing), check vitals, and call your veterinarian. See: The Horse’s Vital Signs and Average Heart Rate.

2) How can I tell neurologic ataxia from mechanical lameness?

Lameness is consistent in one limb and often improves with rest. Neurologic ataxia is inconsistent, often involves multiple limbs, and exaggerates on tight circles/backing. If unsure, compare features with our Lameness Guide and call your vet.

3) What simple cranial-nerve checks can owners do safely?

Menace response (blink to hand wave), palpebral blink (tap eyelid corner), and gentle tongue-tone check. Abnormal = clue, not a diagnosis—protect the eye if blinking is poor and contact your vet. Start with Part 1 for anatomy context, then Part 2 for localization.

4) When should I suspect EPM, EHM (EHV-1 neuro), or Wobbler (CSM)?

• EPM: Asymmetric weakness/muscle loss; horse looks different each rein.

• EHM/EHV-1: Sudden hind ataxia + weak tail/urine dribble, often after fever/new arrivals—isolate and call your vet.

• CSM/Wobbler: Fore/hind ataxia with toe-drag, worse on circles/backing; often tall youngsters or older neck OA.

5) What is the ANS “down-shift” and why does it matter for training?

After arousal, healthy horses return to parasympathetic (rest/digest): HR/RR drop, eyes soften, gut sounds resume. Ending sessions here improves learning and recovery. Use a simple 2/5/10-minute post-work check to confirm the glide back toward your horse’s normal numbers (see Vital Signs/HR links above).

6) My horse runs hot but barely sweats—should I worry?

Yes—think anhidrosis. Move to shade, rinse–scrape cycles, offer cool water/electrolytes per vet advice, and stop work. If recovery is slow or this repeats, contact your veterinarian.

7) What’s the difference between UMN and LMN signs?

UMN = long/weak “loose” strides with delayed placing, worse on circles/backing; reflexes normal/↑; atrophy late.

LMN = true weakness with short/choppy stride, atrophy, and reduced reflexes. Share your videos so your vet can localize.

8) Do vitamin E levels matter for young, clumsy horses?

They can. Low natural-source vitamin E is linked with EDM/EDX patterns (symmetric ataxia in youngsters). Ask your vet about α-tocopherol testing and appropriate formulation/dose—don’t self-dose blindly.

9) Which vital signs help me judge urgency?

Temperature, heart rate, respiration, mucous membranes, and gut sounds. Compare to your horse’s normal baselines, not generic numbers. Start here: Vital Signs and Average HR.

10) Is it ever safe to keep riding a horse with mild neuro signs?

Riding any horse with confirmed or suspected neurologic deficits carries fall risk for horse and rider. Pause ridden work and seek a veterinary assessment to discuss grading, prognosis, and safety.

11) How should I film for my vet?

Level, non-slippery surface. Short clips of straight line (side and rear views), small circles each way, backing 4–6 steps, and a close-up of the eyes/face during simple checks. Add a brief note with first abnormal day, fever/travel/new horses, shoeing changes, and medications.

12) Where do I continue learning on your site?

Start with Part 1 – Overview for labeled anatomy and the functions-by-region table, then go to Part 2 – Diving Deeper for localization, screening flow, and case patterns.