unit 5

CHAPTER 15: AUTONOMIC NERVOUS SYSTEM (ANS)

1. Functions of the ANS

The autonomic nervous system (ANS) regulates involuntary physiological processes, including:

  • Heart rate and blood pressure

  • Digestion

  • Respiratory rate

  • Glandular secretion

  • Body temperature regulation

  • Pupil size

Key Role

  • Maintains homeostasis

  • Works through visceral reflexes

  • Uses a two-neuron chain:

    • Preganglionic neuron

    • Postganglionic neuron

Divisions of the ANS

1. Sympathetic Division (“Fight or Flight”)

  • Activated during stress, danger, or exercise

  • Prepares body for energy expenditure

Major Effects:

  • ↑ Heart rate and blood pressure

  • Dilates bronchi

  • Dilates pupils

  • ↓ Digestion

  • Mobilizes glucose

2. Parasympathetic Division (“Rest and Digest”)

  • Active during calm/resting states

  • Conserves energy and promotes maintenance

Major Effects:

  • ↓ Heart rate

  • Constricts pupils

  • Stimulates digestion

  • Promotes gland secretion

2. Sympathetic vs Parasympathetic (Detailed Comparison)

A. Origins

  • Sympathetic: Thoracolumbar (T1–L2 spinal cord)

  • Parasympathetic: Craniosacral

    • Cranial nerves (III, VII, IX, X)

    • Sacral (S2–S4)

B. Anatomy & Ganglia

Feature

Sympathetic

Parasympathetic

Preganglionic fiber

Short

Long

Postganglionic fiber

Long

Short

Ganglia location

Near spinal cord (sympathetic chain)

Near/in target organ

Divergence

High (widespread effect)

Low (localized effect)

C. Neurotransmitters

Neuron Type

Sympathetic

Parasympathetic

Preganglionic

Acetylcholine (ACh)

Acetylcholine (ACh)

Postganglionic

Mostly Norepinephrine (NE)

Acetylcholine (ACh)

D. Receptors

  • Cholinergic receptors: bind ACh

    • Nicotinic (ganglia)

    • Muscarinic (target organs)

  • Adrenergic receptors: bind NE/Epinephrine

    • Alpha (α)

    • Beta (β)

E. Effects on Target Organs

Organ

Sympathetic

Parasympathetic

Eye

Dilates pupil

Constricts pupil

Heart

↑ rate & force

↓ rate

Lungs

Bronchodilation

Bronchoconstriction

Digestive

Inhibits

Stimulates

Bladder

Relaxes

Contracts

3. Blocking Agents

Cholinergic Blocking Agents

  • Block acetylcholine (ACh) at receptors

  • Inhibit parasympathetic effects

Example:

  • Atropine

    • Increases heart rate

    • Reduces secretions

Adrenergic Blocking Agents

  • Block norepinephrine (NE) or adrenergic receptors

  • Reduce sympathetic effects

Example:

  • Beta-blockers (e.g., propranolol)

    • Lower heart rate

    • Reduce blood pressure

CHAPTER 16: SPECIAL SENSES

1. Sensory Receptors

By Stimulus Type

Receptor

Function

Example

Chemoreceptors

Detect chemicals

Taste, smell

Mechanoreceptors

Detect pressure/stretch

Hearing, touch

Nociceptors

Detect pain

Tissue damage

Thermoreceptors

Detect temperature

Skin receptors

Photoreceptors

Detect light

Retina

By Adaptation Speed

Type

Function

Tonic

Slow adapting (constant stimulus awareness)

Phasic

Fast adapting (detect changes)

2. Eye Anatomy & Functions

Tunics (Layers)

Fibrous Tunic (Outer Layer)

  • Sclera: white, protective

  • Cornea: transparent, bends light

Vascular Tunic (Middle Layer)

  • Choroid: blood supply, absorbs light

  • Ciliary body: controls lens shape

  • Iris: colored part, controls pupil size

Sensory Tunic (Inner Layer)

  • Retina: contains photoreceptors

Key Structures

Anterior Segment

  • Filled with aqueous humor

  • Includes:

    • Anterior chamber (cornea → iris)

    • Posterior chamber (iris → lens)

  • Canal of Schlemm: drains fluid

Posterior Segment

  • Filled with vitreous humor

  • Maintains eye shape

Lens System

  • Lens: focuses light

  • Ciliary muscle: changes lens shape

  • Suspensory ligaments: attach lens

Retina Details

  • Rods: low light, black/white

  • Cones: color, sharp detail

  • Fovea centralis: highest acuity

  • Macula lutea: central vision

  • Optic disc: blind spot

  • Optic nerve: carries signals to brain

3. Vision (Rods, Cones, Pigments)

  • Light activates photopigments

    • Rods: rhodopsin

    • Cones: photopsins

  • Light → chemical change → electrical signal

  • Signal → optic nerve → brain (visual cortex)

4. Vision Terms & Corrections

Condition

Problem

Correction

Myopia

Nearsighted

Concave lens

Hyperopia

Farsighted

Convex lens

Astigmatism

Uneven cornea

Cylindrical lens

Presbyopia

Aging lens stiffness

Reading glasses

Emmetropia

Normal vision

None

Accommodation

Lens shape change

(normal process)

5. Eye Disorders

Disorder

Cause

Pathology

Cataract

Protein buildup

Cloudy lens

Glaucoma

Fluid buildup

Optic nerve damage

Macular degeneration

Aging/genetics

Central vision loss

Conjunctivitis

Infection/allergy

Inflamed conjunctiva

Night blindness

Vitamin A deficiency

Poor dim vision

Color blindness

Genetic

Cone dysfunction

6. Ear Anatomy & Functions

Outer Ear

  • Auricle (pinna): collects sound

  • External auditory canal: directs sound

Middle Ear

  • Tympanic membrane: vibrates

  • Ossicles:

    • Malleus

    • Incus

    • Stapes

  • Eustachian tube: equalizes pressure

  • Oval window: transmits vibrations

  • Round window: releases pressure

Inner Ear

Cochlea (Hearing)

  • Contains organ of Corti

  • Hair cells = receptors

Vestibular Apparatus (Balance)

  • Utricle & saccule: linear movement

  • Semicircular canals: rotation

  • Macula: detects gravity/position

  • Crista ampullaris: detects rotational movement

7. Hearing Sequence (Step-by-Step)

  1. Sound waves enter auricle

  2. Travel through auditory canal

  3. Tympanic membrane vibrates

  4. Ossicles amplify vibrations

  5. Stapes pushes oval window

  6. Fluid waves in cochlea

  7. Hair cells in organ of Corti bend

  8. Signal sent via vestibulocochlear nerve

  9. Brain interprets sound

8. Equilibrium (Balance)

Static Equilibrium

  • Detects head position and linear acceleration

  • Structures:

    • Utricle

    • Saccule

    • Macula

Dynamic Equilibrium

  • Detects rotational movement

  • Structures:

    • Semicircular canals

    • Crista ampullaris

How It Works

  • Movement → fluid shifts → hair cells bend

  • Sends signals to brain → balance maintained

If you want, I can:

  • turn this into a practice exam

  • give you labeled diagrams

  • or make a 1-page cram sheet for quick review before your test