Chapter 7 (Neurons And The Mind)

split in two parts: 1. central nervous system 2. peripheral nervous system

(brain & spinal cord) - the thinking cells

nerve tissue outside CNS

neurons (nerve cells) - excitable, generates/transmits info.

1. sensory neurons 2. motor neurons 3. interneurons

"info in" - detects signals, sends information to CNS

"info out" - carry info from CNS to effector

"decision" - found in brain & spinal cord - interpret sensory signals, initiate response - 99% of neurons in humans are interneurons

signal goes from finger tip to sensory neuron to interneuron

cell body (contains nucleus) dendrites (huge surface for receiving signals) axon (nerve fiber) single long extension down which a signal travels axon endings: transmit signal

- signal collection - integration of incoming signal and generation of outgoing signal to axon - signal passed to dendrites on another nerve cell or to an effector cell

- keeps energy in axon! - wraps around axon - insulator - insulates outer layer on axon - schwann cell (neuroglial cell) - nodes - gaps - signal moves fast by jumping gaps (100x faster) *think of normal wires, they're covered in insulation *think of basketball, guy throwing balls to other players instead of him doing all the work

action potential

- electrical signal is caused by Na+ and K+ ions crossing a neuron's membrane - at 'rest', the inner surface of membrane is more negatively charged than outer surface - charge difference allows a neuron to react quickly to a signal A neural impulse; a brief electrical charge that travels down an axon. The action potential is generated by the movement of positively charged atoms in and out of channels in the axon's membrane.

ion channels gated ion channels pump (ACTIVE TRANSPORTATION)

- unequal distribution of ions - K+ concentration high on outside of cell - Na+ concentration high on the outside - cell uses energy for pumps to maintain or reset balance *K+ tend to leak out, Na+ leaks in

- neuron receives excited signal - resting state: cell is negative inside, positive outside - depolarization: signal causes Na+ gates to open, these ions rush into cell. inside cell becomes positively charged - repolorization: restoration of resting state - pumps redistribute Na+ and K+ ions - action potential travels along axon like a wave * it's all or nothing!

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

K+ gates open, these ions rush out returning the interior of the cell to a negative charge Return of the cell to resting state, caused by reentry of potassium into the cell while sodium exits the cell.

utilizes differences in Na+ and K+ concentrations to move signal signal strength threshold (all or nothing) refractory period - sustained signals occur as impulses *signal cannot be reversed *increasing stimuli will increase pulse rate but only to a fault

synapse neurotransmitters excitatory synapse inhibitory synapse *any given neuron may have thousands of excitatory and inhibitory synapses - combine effects determines whether an action potential is generated

junction between neuron and other neuron

molecules that CHEMICALLY transmit signals between neurons (are inside synaptic vesicles)

synaptic gap

(DO IT) - smack a n!gga - increases activity of postsynaptic cell (increases likelihood of action potential)

(NO NO) - decrease activity of postsynaptic cell (decreases likelihood of action potential)

transport proteins *facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

- once used neurotransmitters must be removed from synaptic cleft (system must be reset and you can fire again) - many different types (enzymatic removal) - activity often determined by presence of receptors on 'receiving' neuron

- serotonin: obsession, compulsion, memory - norepinephrine: alertness, concentration, energy - dopamine: reward, motivation, pleasure

ION CHANNEL OPENS, SODIUM POURS IN! *they can be pumped back up