Weird body facts

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Sulci -fissures between convolutions of brain

The Nervous System

Central Nervous System Peripheral Nervous System

Brain Spinal Cord Somatic Autonomic

Sensory MotorParasympathetic

Sympathetic

Two divisions: Central nervous system (CNS)- act as a

coordinating centre (brain & spinal cord) Peripheral nervous system (PNS)-

effectors, carry information to and from the CNS. Further divided into

Somatic – control skeletal muscle, bones & skin Autonomic – control internal organs of body

Sympathetic Parasympathetic

Two different types of cells Glial (neurological cells; non-conducting,

offer structural support and metabolism of nerve cells)

Neurons (functional units of nervous system) Three groups

Sensory Neurons Interneurons Motor Neurons

http://www.youtube.com/watch?v=FZ3401XVYww&feature=related

Sensory (Afferent) Neurons INPUT – from sensory organs to brain and spinal cord Sense and relay information from environment to CNS Located in clusters called ganglia

  Interneurons

PROCESSING Link neurons within body Integrate and interpret sensory information and connect

neurons to outgoing motor neurons  Motor (Efferent) Neurons

OUTPUT Relay information to effectors, (muscles, organs, glands;

effectors as they produce responses) away from the CNS

Messages move from dendrite, through the nerve cell body, to the axon

Axons are covered with a myelin sheath (insulation), made by Schwann cells which prevent loss of charged ions from nerve cells

Areas between sections of myelin are called nodes of Ranvier; nerve impulses jump from one node to another, speeding up messages

All nerve fibres found within peripheral nervous system contain a thin membrane called neurilemma which surrounds axon

Neurilemma promotes regeneration of damaged axons

Not all nerve cells contain neurilemma and a myelin sheath

Nerves containing mylenated fibres and neurilemma called white matter due to whitish appearance

Grey matter lack myelin sheath and neurilemma and do not regenerate after injury

The simplest neural circuit is the reflex arc. Reflexes are involuntary. No brain coordination is used. 5 essential components:

Receptor Sensory neuron Interneuron (in spinal cord) Motor neuron Effector

REFLEX ARC

http://www.youtube.com/watch?v=Y5nj3ZfeYDQ

Complete Move Fast! Poster lab write-up

Read pg 354-360 Q’s #7, 9, & 10

The Electrocardiogram (ECG) is used to diagnose heart problems.

The Electroencephalograph (EEG) is used to measure brain-wave activity

Action Potential – the voltage difference across a nerve cell membrane when the nerve is excited

Resting Potential – voltage difference across a nerve cell membrane during the resting stage (usually negative)

Unlike most cells, neurons have a rich supply of positive and negative ions inside and outside the cell

A sodium-potassium pump maintains resting membrane potential after ions “leak” down their concentration gradient

- 3 Na+ ions are actively pumped out while 2 K+ ions are pumped in.

ACTION POTENTIAL• action potentials – the movement of an electrical

impulse along the plasma membrane of an axon.• • that are abrupt, pulse-like changes in the membrane

potential that last a few ten thousandths of a second.

• Action potentials can be divided into three phases: the resting or polarized state, depolarization, and repolarization

• The amplitude of an action potential is nearly constant and is not related to the size of the stimulus, so action potentials are all-or-nothing events.

Depolarization must be completed and the nerve repolarized before the next action potential can be conducted as nerves conducting an impulse cannot be activated until the condition of the resting membrane is restored

This time is called the refractory period (usually 1-10 ms)

 

Action Potential

ION GATES CONTROL THE MOVEMENT OF IONS ACROSS THE CELL MEMBRANE.

The separation of electrical charges by the “polarized membrane” has the ability to do work, expressed in millivolts (mV).

Upon excitation, nerve cell membrane becomes more permeable to Na than K Na ions rush into cell causing depolarization Once voltage inside cell is +ve, then Na gates close

The sodium-potassium pump located in cell membrane restores condition of resting membrane by transporting Na+ ions out of the neuron while moving potassium ions inside the neuron in a ration of 3 Na+: 2K+ ions

ATP fuels the pump

Saltatory Conduction

A nerve or muscle fibre responds completely or not to a stimulus.

Nerves have a threshold level…minimum level of a stimulus required to produce a response.

• Watch Nerve Impulse Animation and make notes

• Synapses - Mouse Party Task: Due Friday June 3rd

• Go to:http://learn.genetics.utah.edu/content/addiction/drugs/mouse.html

– Explore the effects of any three of the following drugs on brain function in mice:

• Heroine, ecstasy, marijuana, methamphetamine, alcohol, cocaine, LSD

– In your own words, explain how the drug affects brain function and draw a labeled diagram of the synapse depicting the effects for each drug

Terminology• Synapse

– Region at which neurons come nearly together to communicate. (neuron or effector organ)

• Synaptic Cleft– Gap between neurons (at a synapse)

– Impulses can not propagate across a cleft

• Synaptic Vesicle– Packets of neurotransmitter in presynaptic neuron

• Presynaptic Neuron– Neuron sending a signal (before the synapse)

• Postsynaptic Neuron– Neuron receiving a signal (after the synapse)

Neurotransmitters

5 general criteria: 1) synthesized and released by neurons 2) released at the nerve terminal in a 'chemically identifiable' form 3) the chemical should reproduce the activity of the presynaptic neuron 4) can be blocked by competitive antagonist based on concentration 5) active mechanisms to stop the function of the neurotransmitter

Classical transmitters are small molecules (often amino acid based)

Non-classical transmitters can be peptides or even gasses

5 Steps of Neurotransmission

1) synthesis of the neurotransmitter

precursors and enzymes should be in the correct place

2) storage of neurotransmitter OR precursor

often stored in presynaptic vesicles

5 Steps of Neurotransmission3) release of the neurotransmitter

generally by vesicle fusion

4) binding to target receptor

ionotropic receptors open ion channels

metabotropic receptors modulate other signals

5 Steps of Neurotransmission5) termination of the signal

active termination caused by reuptake or chemical breakdown*For e.g. acetylcholine is broken down by . . .

passive termination uses diffusion

Types of Neurotransmitters

Acetylcholine + muscles, learning, memory

Serotonin (a derivative of tryptophan)

+ sleep, relaxation, self esteem, too little = depression, perception

Norepinephrine (aka noradrenaline)

+ stress and fight/flight response, sympathetic NS:+BP & heart rate

Dopamine + prolactin (milk production), involved in pleasure, movement

Endorphins (-) pain, involved in pleasure

GABA (gamma aminobutyric acid)

(-) anxiety, too little in parts of brain can lead to epilepsy

Glutamate Most common NT, memory, toxic

Sympathetic component prepares body for stress [neurotransmitter used=norepinephrine]•Diverts blood from internal organs to skeletal muscles, heart & brain

Parasympathetic brings things back to normal [neurotransmitter used=acetylcholine]

•Work in conjunction/opposition to each other

–Ex. “on” / “off” switches

“FLIGHT OR FIGHT RESPONSE”

You come across a bear on your walk to school…what

happens?• Sympathetic nervous system does

what?• Increases heart rate• Increases breathing rate• Dilates bronchioles• Dilates pupils• Inhibits digestion

Acetylcholine – make post-synaptic membrane permeable to Na+

Cholinesterase (enzyme)…breaks down Acetyltcholine...prevents constant depolarization

concentrated in the anterior portion of most animals

brain is covered by meninges three-layer protective membrane forms the

blood/brain barrier determines which chemicals will reach the brain

cerebrospinal fluid surrounds brain and spinal cord acts as a shock absorber and a transportation

medium of materials carries nutrients to brain cells

relays wastes from cells to blood

carries sensory nerve messages from receptors of brain and relays motor nerve messages to muscles organs glands

interneurons are organized into nerve tracts which connect the spinal cord with the brain

dorsal nerve tract brings sensory info into spinal cord

ventral nerve tract carries motor info from spinal cord to peripheral muscles, organs, and glands

comprised of three main regions forebrain midbrain Hindbrain

contains paired olfactory lobes receive info about smells

thalamus (below the cerebrum) relay, consciousness, pain

hypothalamus (below thalamus) (temperature, water, hunger, thirst, sex drive); direct connection between hypothalamus and pituitary connects

nervous system with endocrine system cerebrum (2 hemispheres connected by the corpus callosum,

surrounded by cerebral cortex and divided into 4 lobes: frontal- voluntary muscles, walking, speech, personality,

intellect parietal- touch, temperature awareness, emotion, interpreting

speech occipital- vision and interpreting visual information temporal – vision, hearing, memory, interpretation of sensory

information

http://www.youtube.com/watch?v=YpAe3mk1koQ&feature=related

relays information to sensory areas (connective)

temporal- vision and hearing, linked to memory

Associative cortex: conceptualization, planning, contemplation, memory.

Motor cortex: voluntary movement of skeletal muscles.

Sensory cortex: vision, hearing, smell.

Primitive, controls breathing, heart rate, blood pressure.

Main regions of hindbrain cerebellum, pons, and medulla oblongata

Cerebellum located immediately beneath two cerebral

hemispheres largest section of hindbrain deals with coordination and muscle control.

Pons acts as a bridge. Passes information between two regions of

cerebellum and between cerebellum and medulla

  Medulla oblongata

Acts as connection between peripheral and central nervous system

controls involuntary muscle action diaphragm, heart rate, blood vessel dilation etc.

also acts as coordinating centre for autonomic nervous system.

Sympathetic NS – prepares body for stress

Parasympathetic NS – return body to normal

Check out table

Endorphins bond to sites on pain receptor ganglia (Substania Ganglia…SG).

Opiates simulate natural endorphins (p. 437)

Heroin, codeine, morphine etc…must continue to take in order to keep working (addiction!)

Case Study

Quick quiz Quizzes on a range of bio topics :) Another good quiz A virtual body