NS Review

Nervous system

• Coordinates and regulates the function of all other body systems

• 2 major division– Central Nervous System (CNS)• Brain • Spinal Cord

– Peripheral Nervous System (PNS)• Nerves

– carry sensory info to the CNS– Motor commands from CNS to muscles

Neurons 3 types of neuronsSensory neurons

Take messages to the CNSSensory receptors detect changes in the environment

InterneuronReceive input from the sensory neurons before communicate to

motor neuronMotor neuron

Takes message away from CNS to rest of body (organ, muscle or gland)

Neurons

• Anatomy of a neuron– Cell body– Dendrites• Receive signals from other neurons and send them to

cell body

– Axon• Conducts nerve impulses away from the cell body and

send them toward other neurons

Neurons

• Myelin Sheath– Formed by Schwann Cells around the axon– Gaps between Schwan Cells are called nodes of

Ranvier

– Myelin Sheath gives nerves white colour– Helps protect and insulate the nerve – Helps conduct nerve impulse

Neurons DIAGRAM

Nerve impulse

• Nervous system uses a nerve impulse to send information

• When an axon is not conducting a nerve impulse we call it at resting potential – More negative inside the axon – Positive outside the axon

Nerve impulse Difference in polarity is due to ion

concentrationMore Na+ ions outside the axonMore K+ ions inside the axon

Sodium-potassium pumpsActively transport Na+ out of axon and K+ into axon3 Na+ for every 2 K+

Nerve Impulse Action potential

Rapid change in polarity across the axon Nerve impulse

During an action potential DEPOLARIZATION

Sodium channels open upSodium enters the axonAxon becomes more positive

REPOLARIZATION Potassium gates openK+ moves outside of axonAxon returns to original negative charge

Synapse

• During an action potential the impulse travel along the axon until it reaches the axon terminal

• Here gated Ca+ channels open up and Ca+ enters the axon terminal

• Synaptic vesicles merge with presynaptic membrane and bind with a specific protein receptors

Synapse

• Depending on the type of neurotransmitter and receptor the response of the postsynaptic neuron – Excitation • Action potential occurs

– Inhibition• Action potential does not occur

Types of neurotransmitters

• Acetylcholine – triggers muscle contraction – In the central nervous system, it is involved in

wakefulness, attentiveness, anger, aggression, sexuality, and thirst

• Dopamine – involved in controlling movement and posture– It also modulates mood

Types of neurotransmitters

• GABA (gamma-aminobutyric acid)– GABA contributes to motor control, vision, and

many other cortical function

• Norepinephrine – is important for attentiveness, emotions, sleeping,

dreaming, and learning– Norepinephrine is also released as a hormone into

the blood, where it causes blood vessels to contract and heart rate to increase.

Types of neurotransmitters

• Serotonin – contributes to various functions, such as

regulating body temperature, sleep, mood, appetite, and pain

The Central Nervous System

• Brain and Spinal Cord make up the CNS• CNS controls many bodily functions– Breathing– Heart rate– Body temperature– Blood pressure– Emotions– Memory– Creativity

Functions of Spinal cord

• Provides communication between the brain and the peripheral nerves – Sends sensory information to brain– Realays motor impulses from brain to muscles

• Center for thousands of arc reflexes – Allow nerves and muscles to respond quickly to

dangerous stimuli

The Brain

• The four major parts of the brain (in order of highest to lowest functioning)– the cerebrum – the diencephalon – the cerebellum – the brain stem

The Brain: Major Parts DIAGRAM

The Cerebrum

The cerebrum is the largest portion of the brain.

The cerebrum carries out the higher thought processes required for learning and memory and for language and speech.

The Cerebrum

• Cerebral Cortex– Think layer of gray matter

• Sulci – grooves• Gyrus – folds

The Cerebrum

• Primary Motor Area– Controls skeletal muscles – Each body part is controlled by a certain section

• Primary Somatosensory area– Sensory information from skin and muscles arrives

• Processing CentersWernicke’s Area: understand written and spoken

languageBroca’s Area: speech muscle control

The Diencephalon

The hypothalamus is the integrating center that helps maintain homeostasis by regulating hunger, sleep, thirst, body temperature, and water balance.

The thalamus integrates sensory input from the visual, auditory, taste, and somatosensory systems.

The Cerebellum The cerebellum receives sensory input from

the joints, muscles, and other sensory pathways about the present position of body parts.

It also receives motor output from the cerebral cortex about where these parts should be located.

The cerebellum maintains balance and posture.

The Brainstem The brain stem contains:

Midbrain: relay station

Pons: bundles of axons traveling b/t cerebellum and rest of brain

medulla oblongata: contains a number of reflex centers for regulating heartbeat, breathing, and blood pressure.

The Brain DIAGRAM

The Brain

• The brain is divided into 2 cerebral hemispheres– Left hemisphere– Right hemisphere

• Hemispheres communicate with each other though a bridge of white matter called corpus callosum

The Brain

• Brain divided into 4 lobes– Frontal Lobe• reasoning, motor skills, higher level cognition, and

expressive language. – Parietal Lobe• Sensory information

– Temporal Lobe• Hearing, formation of memories

– Occipital lobe • Vision, interpreting vision

Lobes of the brain DIAGRAM

The Limbic System

Limbic SystemEmotions & higher mental functionsBlends primitive emotions (rage, fear, joy, sadness)

with high mental functions (reason, memory)

The Limbic system

• Anatomy– Hippocampus• Involved in storage of long-term memory

– Injured cannot form new memories

– Amygdala• Allows us to feel certain emotions and to perceive

them in other people– This includes fear and the many changes that it causes in the

body

Memory

• Types of memory– Short-term memory• This ability to hold on to a piece of information

temporarily in order to complete a task • It holds a small amount of information (typically around

7 items or even less) • readily-available state for a short period of time

(typically from 10 to 15 seconds, or sometimes up to a minute).

Memory

• Long-term memory– anything you remember that happened more than

a few minutes ago– Long-term memories can last for just a few days,

or for many years

Memory

– Semantic memory • General knowledge about the world

– Names of colours, capital of Canada– Basic facts that have been collected over lifetimes

– Episodic memory • recollection of specific events, situations and experiences

– Skill memory• Involved in performing skills

– Riding bike, playing hockey, using a keyboard• Skills that become automatic or learned

RETREIVING MEMORY Retrieval cues are stimuli that help the process of retrieval

Associations Priming - recalling a particular word becomes easier if another, related word is

recalled first

ContextPeople can often remember an event by placing themselves in

the same context they were in when the event happened.Mood

If people are in the same mood they were in during an event, they may have an easier time recalling the event

Cranial Nerves

Somatic Nervous System

• responsible for carrying motor and sensory information both to and from the CNS

• Responsible for all voluntary muscle movements and processing sensory information (hearing, touch, sight)

• Made up of nerves that connect to skin, sensory organs and skeletal muscles

Autonomic Nervous System

• regulates the functions of our internal organs like the heart, stomach and intestines.

• We are often unaware of the ANS because it functions involuntary and reflexively

• 2 divisions– Sympathetic – Parasympathetic

ANS

• The ANS is most important in two situations:– In emergencies that cause stress and require us to

"fight" or take "flight" (run away)– In non-emergencies that allow us to "rest" and

"digest."