Nervous System

What does the nervous system do

Stimulus → Sensory input → CNS Processing → Motor output → Response

2 parts of the Nervous system

CNS = Brain + Spinal cord

PNS = nerves connecting body to CNS

Cerebral cortex

White matter → Communication (myelinated axons)

Grey matter → processing (nerve cell bodies)

Decides body movement

Basal ganglia/nuclei

Execute smooth movement

Millions of nerve cell bodies

Diencephalon

Thalamus

Epithalamus

Hypothalamus

Pituitary gland

Master gland

Produces hormones

Vertebral column

Cervical

Thoracic

Lumbar

Sacral

Coccygeal

Atlas and Axis

First two vertebrae

Support the head

Flexibility of vertebrae

Intervertebral discs

Muscles and ligaments

Parts of an individual vertebra

Dorsal → Spinous process

Middle → Vertebral canal

Ventral → Vertebral body

Sides → Transverse process

Intervertebral foramen

Opening between adjacent vertebrae

Spinal cord

Outer → White matter

Inner → Gray matter

Dorsal root → Sensory neuron

Ventral root → Motor neuron

Afferent

Arrives to CNS

Efferent

Exists CNS

How is CNS protected

Bones

Meninges

Cerebral spinal fluid

Meninges

Dura mater

Arachnoid

Sub arachnoid

Pia mater

Ventricles

Lateral ventricles

Third ventricle

Fourth ventricle

Cerebrospinal fluid

Made in choroid plexus

Arachnoid villi

Drain CSF from sub-arachnoid space into venus blood

Epidural injection

Needle injected into epidural space

Spinal tap diagnoses

Meningitis

Subarachnoid hemorrages

Encephalitis

Guillain-Barre syndrome

Multiple sclerosis

Resting membrane potential is maintained by

Selective premeability

Ion pumps

Large anions trapped on inner surface of membrane

Selective permeability

Passive diffusion

Permeable to K

Barely permeable to Ca, Na, Cl

Ion Pumps

3 Na out

2 K in

Requires lots of energy

Large anions trapped on inner surface of membrane

Things trapped in the phosphomembrane of cell

Excitable cells

Skeletal muscle cells

Smooth muscle cells

Cardiac muscle cells

Neurons

Non-excitable cells

Red blood cells

Epithelial cells

Generation of Action Potentials (AP) in neurons

Depolarization

Repolarization

Hyperpolarization

Refractory period

Depolarization

Initial depolarization (stimulation) reaches threshold provoking opening of Na voltage gated channels

Influx if Na and rapidly close

Repolarization

K voltage gated channels open

Outflow of K

Hyperpolarization

K voltage gated channels close

Excess outflow of K

Refractory period

RMP restored through diffusion of Na/K pump

Neurons cant be restimulated until restored

Synaptic transmission

Presynaptic neuron releases neurotransmitters from axon terminal

Neurotransmitters in synaptic gap

Neurotransmitters attach to receptors on postsynaptic neuron to transfer nerve impulse

General mechanism of action in neuromuscular synapse

AP from pre-synaptic neuron

AP opens Ca voltage gated channels → Ca influx into presynaptic neuron

Ca triggers ACh exocytosis

ACh binds to specific receptors

Depolarization of post-synaptic neuron → Na channels open and Na flows in

Neurotransmitter inactivated

How the nervous system transduce a response

Stimulus → Sensory neuron → Dorsal root → Spinal cord → Brain → Motor neuron → Ventral root → Neuromuscular junction → Muscle contraction