chapter 7: nervous system neurons and synapses

what are the functions of the nervous system

major control system,rapid electrical sgnals for communication, chemical communication too: neurotransmitter, key role in maintaining homeostasis of most physiological variables, sensation, and movement

What is the nervous system ?

organ system consist of trillions of cells in brain, spinal cord, and periphery

what are the two divisions of the nervous system

central nervous system and peripheral nervous system

what does the central nervous system consist of ?

brain and spinal cord

What does the peripheral nervous system consist of?

autonomic nervous system and somatic nervous system

what are the two sections of the autonomic nervous system

sympathetic and parasympathetic

how many cranial and spinal nerves are there ?

12 cranial, 31 spinal (pairs)

what is the function of the somatic nervous system

controls skeletal muscles

what is the function of the autonomic nervous system

controls smooth and cardiac muscle and glands

what is th function of the parasympathetic system

rest and digest

what is the functions of the sympathetic nervous system ?

fight or flight

what is a neuron

nerve cell basic structure and functional unit

what is the function of a neuron

carries infomation in the form of electrical signals that move along the cell and to adjacent cells

what is a nerve

group of neurons

What is a glial cell?

supporting cells, help neurons function

what kind of neurons are in the cental nervous system ?

interneurons

what kinf of neurons are in the PNS ?

afferent neurons into the CNS

efferent neurons projecting out of the CNS

what di schwan cells form ?

form myelin (fatty sheath) on PNS axons

what do oligodendrocytes form ?

myelin sheath in CNS

true or false: myelinated neurons conduct action potential less rapidly than nonmyelinated neurons

false: myelinated sheaths conduct action potential more rapidly than nonmyelinated neurons

what is afferent (sensory) neuron ?

carries information from tissues and organs o the CNS

what is efferent (motor) neuron ?

carries information from the CNS to effector cells

what is interneuron (association neuron) ?

connects neurons within the CNS

whaty is the resting membrane potential of a neurons ?

-70 mV

what ions are more concentrated outside the neuron ?

sodium ion (Na+) and chloride ions (Cl-)

what ions are more concentrated inside the neuron ?

Potassium (K+)

what are some reason that the resting membrane potential is -70 ?

due to leak channels in the membrane, fixed anions in the cell, and sodium-potassium pump in the membrane

What is ion gating?

opening and closing of gated ions channels. changes permability and polarization

What is depolarization?

membrane potential becomes more positive

why does the membrane potential become more positive

due to positive ions entering cell (when Na+ channels open) and excitatory can result in action potential

what is hyperpolarization ?

membrane potential becomes more negative

Why does hyperpolarization occur?

due to positive ions leaving the cell (when K+ channels open) or negative ions entering cell and inhibitory

What is repolarization?

return to the resting membrane potential (when K+ channels are opn and then start to close)

what causes the initial depolarization in a neuron ?

the initial depolarization is caused by neurotransmitter binding to receptors on dendrites, resulting in a graded potential

what is the threshold potential for an action potential to be generated in a neuron

threshold potential is -55mV

what happens when the threshold potential of -55mV is reached in a neuron ?

voltage-gated Na+ channels open in the axon, allowing Na+ to rush into the neuron causing a large depolarization and an action potential that reaches +30mV

what happens to Na+ channel during an action potentil after they open ?

Na+ channels quickly become inactivated after opening

what role do K+ channels play during an action potential ?

after Na+ channels are inactivated K+ channels open, allowing K+ to exit the neuron. this causes the potential to become more negative, leading to hyperpolarization and then repolarization

what is the main difference between gated and leak K+ channels ?

Gated K+ channels are closed at rest, while leak K+ channels are always open, contributing to greater permability go K+ at rest

what happens to the K+ channels after repolarization ?

the K+ channels close after repolarization is complete

what is the resting state of Na+ channels ?

Na+ channels are closed at rest

what is the state of th Na+ channel at the resting membrane potential ?

at the resting membrane potential the Na+ channel is closed

what triggers the openin of the Na+ channel?

depolarization triggers the opening of the Na+ channel

what is the Na+ channel inactivated

the Na+ channel is inactivated during he refractory period

what is the definition of action potential (AP)

AP is a large depolarization to +30mV which is an electrical impulse that travels along the axon

what is the primary mechanism for communicayion in the nervous system, especially for long distance signaling ?

the propagation of action potential (APs) is the primary mechanism for communication in the nervous system particulary for long distance signaling

how long does action potential typically last ?

1-4milliseconds

what is the all or none principle of action potential

mean that once the theshold potential is reached an action potential wil always occur fully;there are no partial action potentials

where does an action potential occur in the neuron?

an action potential occurs in the axon and travels along the axon

what is the threshold potential required for an action potential to occur ?

the threshold potential is approximately -55mV

what happens when the threshold potential is reach in an action potential ?

when the threshold potential is reach Na+ channels open, Na+ rushes in depolarizing the neuron and the action potential occurs

What is the absolute refractory period?

membrane cannot produce another AP because Na+ channels are inactivated

What is the relative refractory period?

occurs when K+ channels are open and neuron is hyperpolarized: requires stronger stimulus to reach threshold

What is saltatory conduction?

in an myelinated axon, Aps jump from one node of ranvier. ion channels are abundant at the nodes

What is a synapse?

Junction between a neuron and effector cell, where a presynaptic neuron influences the electrical and chemical activity of a postsynaptic neuron or effectors cell ( in muscle or gland)

What is a presynaptic neuron?

Neuron undergoing APs in its axon. It send the excitatory or inhibitory message (NT) to another neuron

What is a postsynaptic neuron?

Neuron that receives the message from an other neuron via the synapse. It is either excited (depolarized) or inhibited (hyper-polarized) by its message

What is a neurotransmitter ?

Chemical messenger released from presynaptic neuron to cause a response in postsynaptic neuron