Autonomic Motor System

ANS= Visceral Motor System

innervate smooth and cardiac muscle, and glands

make adjustments to ensure optimal support for body activites

subconcious

Part of the motor system of the Nervous System - Slide 3

• Parasympathetic and Sympathetic divisions

• Cardiac, smooth, glands

• Differs from somatic nervous system (skeletal muscles)

Two-neuron Chain for ANS Pathway

1. Preganglionic neuron`

2. Postganglionic (ganglionic neuron)

Preganglionic neuron

• Thin

• Lightly-myelinated preganglionic axon

  • Short distances

• Release Ach

Postganglionic (ganglionic) neuron

• In autonomic ganglion outside of CNS

• Nonmyelinated postganglionic axons

  • Extends to effector organ

  • Short distances

• Release Norepinephrine (NE) or Ach

Somatic nervous system vs ANS

• Somatic

  • all somatic motor neurons release acetylcholine (ach)

  • effects always stimulatory

• ANS

  • Preganglionic- release ach

  • Postganglionic- release either norepi(NE) or ach

  • Simulatory or inhibitory depending on receptor type

2 divisions of ANS

1. Sympathetic

2. Parasymphathetic

• All visceral organs served by both divisions but cause opposite effects (DUAL INNERVATION to maintain homeostasis)

Parasympathetic system

1. Promotes maintenance activities

2. Conserves Body energy (digest and rest, defecation)

3. Affect bp, heart rate, repiratory rates, gastrointestinal tract activity high, pupils constricted (close vision)

Sympathetic Division

1. Mobilize body during activity (fight or flight)

2. Exercise, excitement, embarrassment ( inc heat rate, bp, sweaty skin, dilated pupils)

3. During Vigorous physical activity (blood to skeletal muscles and heart, dialte bronchioles, liver releases glucose)

2 types of neurotransmitter fibers

1. Cholinergic Fibers

2. Adrenergic fibers

Colinergic fibers

release ach neurotransmitter

all ans preganglionic axons

all parasympathetic postganglionic axons at effector synapse

Adrenergic Fibers

release NE neurotransmitter

most sympathetic postganglionic axons

exception: sympathetic postganglionic fibers secrete ach at sweat glands

2 Types of Cholinergic receptors bind ACH

1. Nicotinic

2. Muscarinic

Nicotinic Cholinergic receptor

sarcolemma of skeletal muscle cells

• all postganglionic neurons (sympathetic and parasympathetic)

• hormone-producing cells of adrenal medulla

• effect of ach at nicotinic receptors is always stimulatory

• opens ion channels, depolarizing postsynaptic cell

Muscarinic Cholinergic receptor

all effector cells stimulated by postganglionic cholinergic fibers

• effect of ach at muscarinic receptors

• can be either inhibitory or excitatory

• depends on receptor type of target organ

2 classes of Adrenergic receptors

1. Alpha (subtypes a1, a1)

2. Beta (subtypes b1, b2)

• effects of ne depend on which subclass of receptor predominates on target organ

5 drugs that affect receptors

1. Atropine

2. Neostigmine

3. Over the counter for colds, allergies, nasal congestion

4. Albuterol

5. Propanolol- beta block

Atropine

anticholinergic

blocks muscarinic ach receptors

used to prevent salivation during surgery, and to dilate pupils for examination

NEOSTIGMINE

• inhibits acetylcholinesterase that breaks down ach

• used to treat myasthenia gravis

OVER-THE-COUNTER DRUGS FOR COLDS, ALLERGIES, AND NASAL
CONGESTION

stimulate a-adrenergic receptors

leads to decreased mucus production

Albuterol

drugs that attach to b2 receptors to dilate lung bronchioles in

asthmatics

enhance sympathetic activity – stimulate receptors

PROPANOLOL – BETA BLOCKER

treat high blood pressure, severe chest pain and other cardiovascular abnormalities – slows down heart rate

decrease sympathetic activity

Control of ANS Function

hypothalamus—main integrative center of ans activity

subconscious cerebral input via limbic system structures on hypothalamic centers

other controls come from cerebral cortex, reticular formation, and spinal cord

HYPOTHALAMUS

main integrative center of ans activity

Hypothalamic Controls

control may be direct or indirect (through reticular system)

centers of hypothalamus control

heart activity and blood pressure

body temperature, water balance, and endocrine activity

emotional stages (rage, pleasure) and biological drives (hunger, thirst, sex)

reactions to fear and "fight-or-flight" system

Cortical Controls

connections of hypothalamus to limbic lobe allow cortical influence on ans

voluntary cortical control of visceral activities

is possible

biofeedback

awareness of physiological conditions with goal of

consciously influencing them

biofeedback training allows some to control

migraines and manage stress