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general organ system overview and nervous system

How many organ systems does the human body have?


What are the two control systems in the body?

nervous system and endocrine system

Name the organ systems

nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, skeletal, muscular, skin, reproductive

What does the nervous system do?

detects and interprets information from the surrounding information, controls most body functions

What does the endocrine system do?

controls body functions through the use of chemical messengers called hormones

What does the circulatory system do?

brings needed materials to the cells and carries away waste materials

What does the lymphatic system do?

recaptures and filters fluid from the tissues and returns it to the blood stream

What does the respiratory system do?

takes oxygen into the body and releases carbon dioxide

What does the digestive system do?

takes food into the body, breaks it down, and absorbs the nutrients from the food

What does the urinary system do?

removes wastes from the blood

What does the skeletal system do?

supports the body, protects it, and allows movement (along with the muscular system)

What does the muscular system do?

makes it possible for the body to move

What does the skin do?

protects the body and helps regulate body temperature

What does the reproductive system do?

produces the cells necessary to produce offspring

Define "neurons"

nerve cells; highly specialized cells that curry impulses (electrical signals) between body parts

Describe the structure of a neuron

consists of a cell body, dendrites, nucleus, and axon

What is another name for the cell body?


Describe the cell body of a neuron

has nucleus, ribosomes, mitochondria, and all the rest of the organelles

How are neurons different from other cells?

soma has structures sticking off of it in all direction

Define "process" (neuron) and describe the two processes.

anything that sticks off something else
- dendrites: several
- axon: only one

Describe the direction in which an impulse travels through a neuron.

starts at dendrite, then cell body, then axon

When is a neuron polarized?

when a neuron is resting/not carrying an impulse

What does it mean when a neuron is polarized?

- different on one side of its membrane than the other
- inside of the neuron is negatively charged

Define "resting membrane potential"

(RMP) the inside of the cell is more negative than the outside

What is the usual RMP?

around -70 mV, where the inside of the cells is about 70 mV more negative than the outside of the cell

What are the two membrane proteins that help set up and maintain the RMP?

Na+/K+ ATPase and K+ leak channel

Describe the sodium-potassium pump.

(Na+/K+ ATPase) uses a molecule of ATP to move three sodium ions out of the cell, while simultaneously two potassium ions into the cell; sodium/potassium are charged ions so they cannot reverse, unless there is a channel

Define "leak channels"

potassium channels that are always open and will always allow potassium to leak out of the cells (according to gradient)

How do the protein membrane pumps give neurons a negative charge on the inside?

many positively charged ions are being left out of the cell, which leaves negative charges behind (DNA, RNA, proteins); more negative on the inside

Define "voltage-gated channels"

membranes in the neurons that open when the cell membrane reaches a particular voltage

What is the "threshold potential"?

the potential at which the voltage-gated channels open, which is -50 mV

What are the two types of voltage-gated channels?

sodium voltage-gated channels and potassium voltage-gated channels

What happens when the neuron reaches +35 mV?

the sodium voltage-gated channels close and the potassium voltage-gated channels open

What happens when the neuron reaches -90 mV?

the potassium voltage-gated channels close and the only channels left are the sodium-potassium channels and the leak channels

Define "action potential"

the sequence of events where the neuron varies from negative charge to positive and then to -70 mV

Where does the action potential occur?

occurs only at a small portion of the neuron's membrane

Define "depolarization" and "repolarization"

depolarization: the membrane potential moves in the positive direction
repolarization: the membrane potential returns to its resting value

Describe the "impulse" in a neuron.

one small portion of a neuron's membrane fires an action potential, some of the sodium that rushes in from the opening of the voltage-gated channels travels down the inside of the membrane, bringing the next small portion to the threshold; when threshold is reached, opening of voltage-gated channels occur and that portion of the membrane has an action potential, etc. all the way to the axon

What are "Schwann cells"?

special cells that wrap the axon

What is the "myelin sheath"?

the Schwann cell wrapping of the axom that helps increase the speed at which an impulse can travel down the axon because not all portions of the axon have to fire an action potential

What are the spaces between the Schwann cells called?

nodes of Ranvier, which are the only portions of the axon that fire action potentials

What is the "saltatory conduction"?

the jumping type of conduction

What is the refractory period and what does it do?

that short moment when a portion of the membrane is not able to fire a second action potential (until the sodium and potassium channels reset and membrane is at resting potential), which ensures that the action potential will only travel in one direction down the axon

What happens when the impulse reaches the end of the axon?

the impulse will either get transferred to another neuron's dendrites or to an organ

What is a "synapse"?

the point where the impulse gets transferred, nothing more than a neuron-to-neuron junction or a neuron-to-organ junction

What is a "neurotransmitter"?

a special chemical that passes the impulse from one neuron to the next

What is the most common neurotransmitter?


Define "synaptic cleft"

the small gap between the first neuron and the second neuron

Describe the terminal end of the axon of the initial neuron and the dendrites of the second neuron.

the terminal end of the axon has vesicles that contain the chemical neurotransmitter and the dendrites have receptors that can bind to the neurotransmitter

Describe the process of transmitting an impulse.

when the impulse reaches the terminal end of an axon, causes the vesicles to fuse with the cell membrane; neurotransmitter released into the synaptic cleft by exocytosis; diffuses instantly across the synaptic cleft and binds to the receptors

What are the receptors in the dendrites connected to?

ion channels

What would happen if ion channels allowed sodium to enter the neuron?

depolarizes, which causes voltage-gated channels to open, causing an action potential to fire

What does it mean when a neuron is stimulated?

depolarize toward threshold

What does it mean when a neuron is inhibited?

a neurotransmitter causes a cell to move away from the threshold

What happens when a neuron receives stimulatory and inhibitory inputs at the same time?

summation: add up the two inputs and see which one has more input

What is the "central nervous system"?

(CNS) the brain and spinal cord, which are made completely out of neurons

What is the peripheral nervous system"?

(PNS) neurons outside of the brain and spinal cord, like organs and skin

How do the CNS and the PNS cooperate?

the PNS carries out sensory information to the CNS, where it is processed and integrated with other information; afterwards, the CNS sends out reactions

What are the three types of neurons in the nervous system?

sensory, motor, and interneurons

Define "sensory neurons"

neurons involved in sending information to the CNS from the sensory organs of the body

Define "motor neurons"

neurons involved in sending information from the CNS to the organs of the body

Define "interneurons"

neurons that are completely within the brain and spinal cord, which often connect sensory and motor neurons

neurons in the PNS

sensory and motor

neurons in the CNS


What are the different types of action potential?

all action potentials are the same (in every way)

How does the brain determine the strength of sensations?

the frequency of action potentials; the more action potentials, the stronger, whereas the less action potentials, the weaker

What are the subdivisions of the nervous system?

spinal cord, cerebrum, cerebellum, medulla, hypothalamus

spinal cord

primarily involved in primitive, reflex actions


the cerebral cortex is the conscious mind, where voluntary actions occur (movement, speech, problem solving), and we get conscious awareness of sensations


coordinates muscle movement and balance so that the movement is smooth and coordinated


involuntary acts originates here (breathing/blood pressure regulation); relatively primitive


maintains body homeostasis - constant internal environment regardless of changing external conditions - monitors things like hormone levels, electrolyte balance, and temperature

subdivisions of the PNS

somatic and autonomic nervous systems

somatic nervous system

(SNS) a voluntary system, meaning that we have conscious control over the organs - uses skeletal muscles

neurotransmitter in somatic nervous system

acetylcholine (ACH), which causes muscle to depolarize and contract

autonomic nervous system

(ANS) involuntary system, meaning we do not have control of the organs

subdivisions of autonomic nervous system

sympathetic and parasympathetic division

sympathetic division

increases body activity "fight or flight" - helps prepare body for stress situations by increasing heartbeat, blood pressure, breath rate, diverting blood flow away from digestive organs and toward skeletal muscles

parasympathetic division

decrease body activity "resting and digesting" - most active when you are at rest by decreasing rate and force of heartbeat, decreasing blood pressure, decreases breath rate, and diverts blood flow to the digestive organs and away from skeletal muscles - increases digestive activity

neurotransmitter in sympathetic division


neurotransmitter in parasympathetic division


epinephrine (adrenaline)

one of the first things triggered by the sympathetic system is the release of this hormone from the adrenal medulla - similar to norepinephrine and causes same effect - because it is a hormone, released into the bloodstream, but norepinephrine is at a synapse - prolongs and enhances the effects of the sympathetic response

vertebrate group

fish, amphibians, and birds

similarities in nervous systems between humans and vertebrate group

CNS made up of brain and spinal cord, nerves transmit impulses to and from the brain and spinal cord make up the PNS

nervous systems of arthropods and annelids

nervous system made up of a ventral nerve cord and a brain; ganglia along the nerve cord and neurons branch from the ganglia


clusters of nerve cell bodies along the nerve cord in arthropod and annelid nervous systems

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