Nervous SystemBy: Ms. Wetherington

Review

• What is a neuron?• Synaps?• Synaptic cleft, pre and post synaptic cells• Myelin Cells– CNS: Oligodendrocyte cells– PNS: Schwann cells

Review

• Resting membrane potential = -70mv• Key Point?*– Sodium potassium pump (ATPase) purpose• Restores gradient after action potential

Signaling review

• Electrotonic potential causes cells to have a strong influx of sodium ions– Quickly diffuses to change membrane potential just

slightly– Changes membrane potential just enough to cause

action potential– Impulse propagation: movement of action potential– Refractory periods?– Salatory conduction?

Types of neurons

• Afferent neurons: carry information from PNS to brain or spinal cord (sensory information)

• Efferent neurons: Carry information from brain/spine to PNS

• Intraneurons: local circuits

Nerves

• Single axons only carry so much information– Nervous system bundles many axons together as

nerves• Can be sensory, motor or mixed

Ganglia and Nuclei

• Somas also cluster – PNS known as ganglia– CNS known as nuclei

Central Nervous System: Brain

Brain

• Consistancy similar to gelatin– Protected by???– Integrates sensory, coordination, motor,

movement, cognition

– Mylenation: white matter– Unmyelinated (somas, dendrites, unmyelinated

axons): Gray Matter

Layout

• Forebrain• Midbrain• Hindbrain

Forebrain

• Most recently acquired part of the CNS in terms of evolution

• Broken down into:– Telencephalon (Cerebrum)• Frontal lobe• Parietal lobe• Occipital lobe• Temporal lobe

– diencephalon

Cerebral Cortex

• Highly convoluted gray matter on brain surface (outermost cerebrum)– Deals with memory, attention, awareness,

thought, language, consciousness

– Each lobe is independent but communicate through corpus collosum (made of white matter)

Frontal lobe• Future consequences from current actions• Good and bad• Long term memory (non-task based) - often

emotions• Modifies for fitting into social norms

Parietal lobe

• Sensory information• Manipulation of objects• Reading• speech

Occipital lobe

• Visuals• dreams

Temporal lobe

• Long term memory• Verbal • language

Diencephalon

• Thalamus and hypothalamus– Thalamus: gateway to brain• Sensory information passed through thalamus before

relayed to cortex

Midbrain

• Relay point between more peripheral structures and forebrain

• Passes sensory information and visuals to forebrain from hindbrain

• Returns motor instructions to hindbrain

Hindbrain

• Structures are seen in many organisms • Responsible for involuntary functions

– Cerebellum– Medulla oblongata– pons

Cerebellum

• Quality control agent: error checking– Checks motor signal in agreement with sensory

information coming into the body– Prevents things like falling by adjusting to new

situations• Balance• Prevents you from looking like an idiot

Medulla oblongata

• Homeostasis– Breathing, heart-rate, blood vessel activity,

swallowing, vomiting, digestion

Pons

• Helps out the medulla oblongata by regulating breathing

Arousal and sleep

• Network called reticular formation regulates sleep and arousal– Pons and medulla contain centers that cause sleep

when stimulated– Milk has lots of tryptophan which can be used to

make serotonin….maybe why you get sleepy when you drink it?

Central Nervous System: Spinal Cord

Spinal cord

• Protected by vertebral column and broken into four parts– Cervical– Thoracic– Lumbar– Sacral

Spinal cord• Contains both gray and white matter like the brain• Axons are for both motor and sensory function– Sensory neurons bring information from PNS and enter the

dorsal (back) side of the spine– Motor neurons exit ventrally– Cell bodies (somas) found in dorsal root ganglia

Peripheral Nervous System

PNS

• 12 pairs of cranial nerves and 31 pairs of spinal nerves

• Made up of: – Somatic nervous system (SNS)– Autonomic nervous system (ANS)

Somatic Nervous System

• Voluntary movement– Release of acetylcholine

from nerve terminal onto muscle leads to contraction

– Binding of acetylcholine leads to muscle depolarizing

– SNS also deals with reflexes (doesn’t go to brain)• Monosynaptic and

polysynaptic

Monosynaptic

• Single synapse between sensory neuron and motor neuron (mono)– Knee jerk– Patellar tendon stretched

and sends information up the sensory neuron to the spine where it meets motor neuron to contract quadriceps• Responding to dangerous

situation

Polysynaptic

• At least one interneuron between sensory and motor neuron– Stepping on a tack– Foot jerks (monosynaptic) but you must balance

on the other leg– To stimulate other leg to have downward motion

internurons must provide connection from sensory information on the leg jerk to the opposite leg

Autonomic Nervous System

• Fight or flight response• Rest and digest response– Known as involuntary nervous system

ANS

• Uses cardiac and smooth muscle– Smooth: blood vessels, bronchi, bladder,

gastrointestinal– ANS also controls blood pressure, ventilation,

urination and digestion

ANS

• 2 neuron system (unlike SNS) which play telephone

• 1st neuron = preganglionic• 2nd neuron = postganglionic – Preganglionic soma is in CNS and the axon travels

to a ganglion in PNS– Synapses with post ganglionic neuron to affect

target tissue

Regulation of ANS

• Can regulate individually or coordinate with both parts:– Sympathetic– Parasypathetic

Sympathetic nervous system

• Stress– Fight or flight

BEAR ATTACK!!!!

BEAR ATTACK!!!

• Increase blood flow to heart and skeletal muscles

• Decrease blood flow to GI tract and kidneys• Ensure proper oxygen to muscles• Pupils dilate so you can keep an eye on the

bear as you run

BEAR ATTACK!!!

• Preganglionic neurons use acetylcholine or epinepherine

• Postganglionic neurons use norepinephrine

Parasympathetic nervous system

• Rest and digest

•

MMMMM PIZZA!!!

Pizza time!

• Increase blood flow to digestive and excretion organs

• Decrease blood flow to skeletal muscles and heart

• Heart rate and ventilation rate decrease– Vagus cranial nerve responsible for many

parasympathetic effects in thoracic and abdominal cavity

– Pre and postganglial neurons both use acetylcholine