The Autonomic/Somatic Nervous system

Two pathways for autonomic nervous system

• preganglionic - myelinated; CNS → autonomic ganglion

• postganglionic - unmyelinated; unmyelinated axon → effector

Sympathetic division pre/post

• preganglionc - short

• postganglionic - long

  • thoracolumbar

Parasympathetic pre/post

• preganglion - long

• postganglionic - short

  • craniosacral

Sympathetic receptor classes

• Adrenergic receptors

  • bind to epinephrine and norepinephrine

Major types of adrenergic receptors

1. Alpha

   • alpha 1

   • alpha 2

2. beta adrenergic

   • beta 1

   • beta 2

   • beta 3

Cholinergic receptors

• bind to ACh

• muscarinic

• nicotinic

Beta 1 function

cardiac muscle cells, certain kidney cells, and adipose cells

Beta 2 function

SKM cells lining airways of respiratory tract, and in wall of urinary bladder, skeletal muscle fibers, cells in liver, pancreas, salivary glands

Beta 3 function

primarily in adipose tissue cells, and SM cells in walls of digestive tract

Muscarinic function

on sweat glands of skin

Nicotinic function

• in plasma mb of all postganglionic neurons

• w/i sympathetic ganglia and adrenal medullae

Classification of sensory receptors

• general senses: somatic and visceral

  • somatic - tactile

  • visceral - info about conditions

Free nerve endings

nociceptors, thermoreceptors

encapsulated nerve endings

pacinian corpuscles, meissner’s corpuscle

What are exteroreceptors?

at/near body surface

What are interoreceptors?

inside body, includes blood vessels, viscera, nervous system

What are proprioceptors

muscles, tendons, joints, inner ear

What is sensory receptor adaptation?

decrease in potentials during a maintained, constant stimulus

What is a rapidly adapting receptor?

receptors that detect pressure, smell, and touch

What are slowly adapting receptors?

receptors that detect pain, body position, and chemical composition of the blood

What are the four somatic sensations?

• tactile

• thermal

• pain

• proprioceptive

What is referred pain?

pain is felt in or just deep to the skin that overlies the stimulated organ or in a surface area far from the stimulated organ

What are prorpioceptive sensations?

• name of receptors in name

• slow adaptation

• weight discrimination

Three types of proprioceptive sensations

• muscle spindles

• tendon organs

• joint kinesthetic

What are first order neurons?

impulses from somatic receptors to the brain stem or spinal cord

What are second order neurons

impulses from the brain stem and spinal cord to thalamus

What are third order neurons

thalamus → somatosensory area cortex on same side

Three main somatic sensory pathways

1. posterior column-medial lemniscus

2. anterolateral (spinothalamic) pathway

3. trigeminothalamic pathway

Nerves that extend out of the brainstem and spinal cord are called what?

low motor neurons (LMNs)

Four somatic motor pathways circuits

• local circuit - located close to LMNs in the brainstem and spinal cord

• upper motor neurons (UMNs) - input to both lower circuit and neurons and LMNs

• basal nuclei neurons - assist movement by indirectly providing input to UMNs

• Cerebellar neurons - assist movement via control of activity of UMNs

Two somatic sensory pathways

1. Direct motor pathways: signals to LMNs from cerebral cortex

2. Indirect pathwaysL signals to LMNs from motor centers in the basal nuclei, cerebellum and cerebral cortex