anatomyI- unit 5

CNS

Brain + spinal cord (central control)

PNS

Nerves outside CNS

Afferent neurons

Carry sensory input to CNS

Efferent neurons

Carry motor output from CNS

Somatic nervous system

Voluntary (skeletal muscle)

Autonomic nervous system (ANS)

Involuntary (smooth/cardiac muscle, glands)

Sympathetic Division

Origin: Thoracolumbar (T1

Preganglionic NT (Sympathetic)

ACh → binds nicotinic receptors on ganglia

Postganglionic NT (Sympathetic)

NE → binds adrenergic receptors (α or β)

Adrenal medulla

Releases epinephrine and norepinephrine into bloodstream

Effect of Sympathetic Division

Long

NE inactivation

Inactivated slowly

E from adrenal prolongs effects

Parasympathetic Division

Origin: Craniosacral (brainstem: CN III, VII, IX, X + S2

Preganglionic NT (Parasympathetic)

ACh → nicotinic receptor on ganglion

Postganglionic NT (Parasympathetic)

ACh → muscarinic receptors on target

Effect of Parasympathetic Division

Short

ACh destruction

Quickly destroyed by acetylcholinesterase

Sympathetic Ganglia Types

1. Sympathetic trunk (paravertebral) 2. Collateral (prevertebral)

Parasympathetic Ganglia Type

Terminal ganglia (near/within organs)

CN III (Oculomotor) Pathway

→ ciliary ganglion → pupil constriction

Vagus Nerve (CN X) Pathway

→ ganglia in thoracic/abdominal viscera

Somatic Reflexes

One motor neuron → skeletal muscle

Visceral Reflexes

Two

Sympathetic postganglionic neurotransmitter

NE (adrenergic)

Parasympathetic postganglionic neurotransmitter

ACh (cholinergic)

Nicotinic Receptors

Always excitatory

found in all ganglia

Muscarinic Receptors

Can be excitatory/inhibitory

on parasympathetic targets

α

adrenergic Receptors

β

adrenergic Receptors

Dual Innervation

Most organs receive input from both systems (usually opposite effects)

Parasympathetic

Localized, short

Sympathetic

Widespread, longer

Hypothalamus

Main control center of the ANS, regulates temp, water balance, hormones, works with limbic system (emotional input)

Brainstem

Includes Medulla (HR, BP, GI activity) and Midbrain (pupil/lens reflexes)

Spinal cord

Controls defecation and urination, can be consciously overridden

Cerebral cortex

Modifies autonomic functions via hypothalamus and limbic system

Hypertension

Overactive sympathetic vasoconstriction, treated with α1 blockers (e.g., Prazosin)

Raynaud's Disease

Vasospasms in fingers/toes due to cold/stress, can be primary (no underlying disease) or secondary (linked to autoimmune disorders)

Symptoms of Raynaud's Disease

Cold, white/bluish fingers, numbness, tingling

Risk factors for Raynaud's Disease

Women, ages 15

Seeing a bear

Sympathetic response: ACh → NE, Nicotinic → Adrenergic (α/β), Effects: ↑HR, dilated pupils, ↓digestion

Post

dinner

Relaxing bath

Parasympathetic response: ACh → ACh, Nicotinic → Muscarinic, Effects: ↓BP, relaxed breathing

Nervous speech

Sympathetic response: ACh → NE or ACh (sweat), Nicotinic → Adrenergic/Muscarinic, Effects: ↑HR, sweat, dry mouth

Rods

Photoreceptors for night vision, black & white, located in peripheral retina

Cones

Photoreceptors for color vision, sharp detail, located in central retina (fovea)

Accommodation

Lens changes shape for near/far vision

Pupil constriction/dilation

Controls light entering the eye

Rhodopsin

Light

Photopsins

Color

Retinal

Light

Color Blindness

Condition caused by missing/dysfunctional cones, usually red

Visual Pathway

Retina → Optic nerve → Optic chiasm → Optic tract → Thalamus → Occipital lobe (visual cortex)

Olfactory epithelium

Contains hair cells, supporting cells, and basal cells for smell

Taste buds

Structures within papillae that include gustatory, basal, and supporting cells

Sound Pathway

1. Auricle → 2. Auditory canal → 3. Tympanic membrane → 4. Ossicles → 5. Oval window → 6. Cochlea → 7. CN VIII → 8. Brainstem → 9. Thalamus → 10. Temporal lobe

Meniere's Syndrome

Condition characterized by vertigo, tinnitus, hearing loss, and nausea

Presbycusis

Age

Tinnitus

Condition characterized by ringing in the ears

Conduction Deafness

Hearing loss due to sound blockage (e.g., wax, fluid)

Sensorineural Deafness

Hearing loss due to damage to nerves or hair cells

Pitch

Frequency of sound

Loudness

Amplitude of sound, measured in dB