Weird body facts
Jan 11, 2016
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