ANS and General and Special Senses

Autonomic Nervous System

The part of the nervous system responsible for the involuntary control of various body systems.

Reflex arc

A sensory integrative motor pathway that controls autonomic reflexes or visceral reflexes.

Parasympathetic

The division of the autonomic nervous system that controls the "rest and digest" response.

Sympathetic

The division of the autonomic nervous system that controls the "fight or flight" response.

Dual Innervation

The presence of both parasympathetic and sympathetic innervation in an organ, allowing for precise control.

Effect on parasympathetic

The overall effect: rest and digest

Effect of sympathetic

The overall effect: fight or flight

Motor/Efferent Pathway of ANS

The two-neuron pathway that carries information from the CNS to effector tissues.

Preganglionic neuron

The neuron that carries impulses from the CNS to the autonomic ganglion.

Postganglionic neuron

The neuron that carries impulses from the autonomic ganglion to the effector tissue in the periphery.

Characteristics of Sympathetic

• short preganglionic axon, long postganglionic axon

• divergence of nerves

• preganglionic cell bodies in spinal cord, postganglionic cell bodies in paravertebral chain ganglia or collateral ganglia

Characteristic of Parasympathetic

• long preganglionic, short postganglionic

• not very divergent

• preganglionic cell bodies in brain stem and sacral spinal cord, postganglionic cell bodies in or near autonomic effectors (organs)

Receptors and Neurotransmitters of ANS

acetylcholine, norepinephrine

Acetylcholine

A neurotransmitter released by cholinergic neurons in the ANS, binds to specific cholinergic receptors

the cholinergic receptors

muscarinic and nicotinic

nicotinic receptors location

on all postganglionic neuron cell bodies in both divisions

muscanaric receptors location

on all effector cells (eg. organs) of parasympathetic division, promotes rest and digest

also on sweat glands in sympathetic, promotes sweat secretion

Norepinephrine

A neurotransmitter released by adrenergic neurons in the ANS, binds to specific adrenergic receptors

the adrenergic receptors

alpha and beta, only in sympathetic system

alpha receptors locaiton

found on smooth muscles of blood vessels, causes vasoconstriction for increase in blood pressure

beta receptors location

beta 1 found on cardiac muscle of the heart

beta 2 found on smooth muscle of bronchioles in lungs

Sympathetic nervous system neurotransmitters

preganglionic: release ACh

postganglioni: mainly NE

• Producing sweat: only when ACh stimulates the sweat glands

Parasympathetic nervous system neurotransmitters

preganglionic: releases ACh

postganglionic: releases ACh

General and Special Senses

The different types of sensory receptors and their functions.

Receptor Potential

The development of a potential in a sensory receptor in response to a stimulus.

Principle of Adaptation

The decrease in receptor potential over time in response to continuous stimuli.

Special Sense Receptors

Receptors that receive input for smell, taste, vision, hearing, and equilibrium.

General sense organs

Widely distributed receptors that sense touch, temperature, and other general sensations.

Free Nerve Endings

The simplest and most widely distributed sensory receptors.

Encapsulated nerve endings

Sensory receptors with a connective tissue capsule surrounding the ends.

• corpuscles for touch, vibrations, etc

• stretch receptors (muscle spindles and golgi tendon)

Classification By Location

exteroceptors (body surface), visceroceptors(internal organs), proprioceptors (tonic and pasic)

By type of Stimulus Detected

mechanoreceptors, chemoreceptors, thermoreceptors, nociceptors, photoreceptors, osmoreceptors

By Selectivity and Sensitivity

thermoreceptor sensitivity, discriminative (fine) touch, cutaneous sensation

Referred Pain

Pain felt in an area of the body that is different from the actual source of the pain.

• from convergence of sensory nerves