Lec: Nervous system

Neuron system cells

Neuron - transmits info. by electrical impulses

Impulse - electrical charges

Cell body - main part of the cell

Dendrites - extension

Axon - extension that sends information

Axon hillock - cone-shaped thickening that leads to axon

Myelinated

has myelin sheaths

• prevent electricity from escaping

Nodes of Ranvier - gaps, accreted the electrical signals

White matter - myelinated axons of CNS

Unimyelinated

no myelin sheaths

Gray matter- unmyelinated axons in the CNS

Multipolar neuron

multiple extensions (many dendrite, 1 axon)

Bipolar neuron

two extension (1 dendrite, 1 axon)

Unipolar

one extension ( one side is dendrite, other side is axon)

Sensory neuron

afferent neuron

• receive input from peripheral body parts from sesnory receptors

• most unipolar, some bipolar

Interneuron

found in brain and spinal cord

• conduct impulses from one part of brian/spinal cord to another

• multipolar

Motor neuron

efferent neurons

• conduct impulses from brain/spinal cord to muscles

• multipolar

Microglial cells

phagocytose bacteria and cellular debris

• blood borne immune cells have limited access to CNS

Oligodendrocytes

provide insulating myelin sheath around axons in PNS

• protect brain and spinal cord

Schwann cells

provide insulating myelin sheath around axons in CNS

Astrocytes

found between blood vessels and neurons of CNS

• regulate nutrient flow

• make up Blood Brian Barrier

Blood Brian Barrier

chemicals flowing into brain are tighely regulated

• population of cells that seperate the blood

Synapse

gap between neuron and another cell

Presynaptic neuron

neuron sending the information

Postsynaptic neuron

neuron receiving the information

Synaptic transmission

sending messages across synapse

Neurotransmitters

chemical signals that travel across synapse to relay information

• release to affect postsynaptic

Dopamine: pleasure, motivation, rewarded behaviors

Serotonin: mood, happiness, regular sleep - exercise and light exposure

Endorphins: euphoria, pain relief - exercise excitement , natural pain killers

Drugs

Cocaine: causes large release of dopamine

Heroin: mimics endorphins

Nicotine: increase levels of dopamine

Ecstasy: excessive release of serotonin

Methamphetamine: causes release of dopamine and norepinephrine (Class 1)

Cell membrane potential

Resting potential - electrical charge difference in a resting nerve cell

• -70 millivolts (mV)

Threshold potential - amount of depolarization at axon hillock before axon fires

• -55 millivolts (mV)

Central Nervous System (CNS)

Composed of the brain and spinal cord

• spinal cord convey info. to brain

Efferent neurons transmit information away from the CNS (body to exit)

Peripheral Nervous System (PNS)

Composed of nerves and ganglia

• afferent neurons transmit info. to the CNS (body to brain)

Motor system - skeletal muscles and is voluntary

Autonomic nervous system - internal environment in involuntary manner

Glia in CNS

Function

• Ependymal cells - promote circulation of cerebrospinal fluid

• micorgilia protect the nervous system from microorganisms

• Astrocytes - provide structural support for neurons and induce formation of BBB

Cranial nerve

in the brain and mostly terminate in organs of the head and upper body

• extend from the brain

Spinal nerves

in the spinal cord and extend to parts of the body below the head

• extend from the spine

Sympathetic division

correlates with the flight-or- fight response

• emergency system

• see-saw effect - one higher than the other

Parasympathetic division

promotes a return to “return and digest”

Enteric division

controls activity of the digestive tract, pancreas, and gallbladder

Brianstem

coordinated and conducts information between brain centers

three parts

1. midbrian - reflex to sound, visual reflex

2. pons - brain stem, breathing center in medulla

3. medulla oblongata - heart, respiratory, life force

Reticular formation

regulates the amount and type of info. that reaches the cerbal cortex and affect alertness

Melatonin

released by the pineal gland and plays a role in sleep cycles

Cerebellum

coordination and error checking during motor, perceptual and cognitive functions

• learning and remembering motor skills

Diencephalon

three regions:

Epithalamus - includes the pineal gland and generated cerebrospinal fluid from blood

Thalamus - main input center for sensory information leaving the cerebrum and output for motor info.

Hypothalamus - regulates homeostasis and basic survival behaviors

Cerebrum

largest and complex part of the brain

• frontal: emotion, thinking

• parietal: sensations

• occipital: vision

• temporal: hearing

Corpus Callosum

provides communication between the right and left cerebral

• right side controls left side of body vice versa ( Lateralization)

Left hemisphere

• more adept at language, math, logic

Right hemisphere

• recognition, nonverbal thinking, emotional processing

Broca’s area

the frontal lobe is active when speech is generated

Wernicke area

area in the temporal lobe when speech is heard

Limbic system

emotions generated, give, long term and into emotion

Amygdala - located in the temporal lobe and helps store an emotional experience as emotion memory

• fear sensing