final biology quiz

6.5 Neurons and synapsis

Central nervous system

• CNS

• Brain and spinal cord

6.5 Neurons and synapsis

Central nervous system

• CNS

• Brain and spinal cord

Peripheral nervous system

• PNS

• every other aspect of the body

neurons

• cells that transmit electrical impulses

• they connect to other cells at a Synapse

• nerve impulses are carried out by temporary shifts in electrical charge

Post synaptic cells may be…..

• another nueron

• effector cell (glands, muscles etc.)

dendrites

• short branched nerve fibers

• many in the brain

axons

• transmit impulses over a long distance

• tips of toes to the spinal cord

• inside of the axon is Negatively charged with respect to the outside

resting potential

• the neuron is not transmitting an impulse

• around -70 mV

Action potential

• rapid change is membrane potential

• occurs in two phases: Depolarization and repolarization

• the charge is changed by moving sodium ions in and potassium ions out of the atom

action threshold

• point to which the neuron reacts

• around -50mV

depolarization

• change from negative to positive

• Na+ flow into the axon

Repolarization

• change back from positive to negative

• K+ ions flow put of the axon

Nerve fibers are…….

• myelinated

• myelin is the membrane of Schwann cells, wrapped around a nerve fiber many times

• myelination insulates the axon, increasing the speed of impulse

• allows for saltatory conduction

Saltatory conduction

• impulses jump from gap to gap

• each gap is called a node of Ranvier

• impulses travel in one direction (never backwards)

Na/K pumps generate…..

• resting potential

• 3 Na+ put and 2 K+ in maintains a concentration gradient

Oscilloscope traces

• nerve impulses work on an all or none principle

• impulse is only initiated if threshold potential is met

• impulse is carried node to node due to action potentials being propagated along the axon

local currents

• when ions migrate laterally

• provide the threshold potential to open the voltage gated Na+/k+ channels

Synapse

• are junctions between cells in the nervous system

synapses exist between:

• neuron-neuron

• neuron-receptor cells (sensory reception)

• neuron- effector cells (responds to a stimulus)

Synapse step 1

• Pre-synaptic neurons are depolarized, and release a neurotransmitter into the synapse

Synapse step 2

depolarization opens voltage gated calcium channels

• calcium influx signals synaptic vesicles to fuse with pre-synaptic membrane, releasing neurotransmitter by exocytosis

Synapse step 3

• Acetylcholine diffuses across synaptic cleft and binds to receptor proteins on postsynaptic membrane

• this binding opens sodium ion channels and an action [potential is initialed in the postsynaptic neuron

synapse step 4

after Acetylcholine binds to receptor, it is rapidly broken down by the presynaptic neuron

• this is Cholinergic synapse, since acetylcholine is the active neurotransmitter

6.6 muscles and movement

sessile animals

are tethered to one location

motile animals

move free through the environment

mucles work in

• antagonistic pairs to perform opposite movements

• ex: biceps flex and triceps extend

• joints have adaptations to reduce friction between bones

anantomy of the hip joint

bones- femur and pelvis

ligaments- connect these bones

tendons- connect the bones to the muscles for movement

cartilage- protects the areas of contact

synovial fluid- is held within a joint capsule. and it lubricates the joint to reduce friction

muscle system

Muscles are like the organ

firbers= cells

myofibril= subcellular

sarcomere= protiens

Sarcomere

sliding filament theory

neuronmuscular junction

• A motor neuron synapse with a muscle fiber to initiate movement

• acetylcholine is released and binds to r3ecptors on muscle fiber

• the muscle then releases calcium to initiate contraction

Step 1 and 2

• myosin heads hydrolyze ATP and become reoriented and energized (in the right position)

• myosin heads bind to the actin forming cross bridges (they are connected)

step 3

• myosin head rotates toward the center of the sarcomere (power stroke)

• this is its natural position

step 4

• myosin heads bind ATP, the cross bridges detach from the actin

• bond broken and now it’s in its start position

the caclium released in synapse binds to …….

• troponin

• troponin moves tropomyosin aside exposing the binding sites

• these binding sites allow for crossbridges to form

cardiac muscle vs skeltal muscle

cardiac muscle:

• short, fewer nuclei, branched, connected by intercalated discs, has sarcomeres but less pronounced

skeletal muscle:

• long, many nuclei, has dark pronounce sarcomeres

titin

• a massive protein in the sarcomere that recoils after contraction

• prevents overstretching

• the recoiling action helps antagonistic muscle movements