Homeostasis (NERVOUS SYSTEM) Flashcards
What are the 2 divisions of the Nervous System? Explain each.
- Central Nervous System (CNS)
~ consists brain, spinal cord
~ integrates & processes info sent by nerves - Peripheral Nervous System
~ includes nerves that carry sensory messages to CNS
~includes nerves that send info from CNS to muscles & glands
BOTH SYSTEMS WORK TOGETHER TO CONTROL SENSORY INPUT, INTEGRATION, AND MOTOR OUTPUT
What is norepinephrine/noradrenaline? What happens when there’s an imbalance?
readies the body to respond to danger or other stressful situations; plays a role in the body’s “fight or flight” response (helps with alertness, attention)
too little = hunger cravings, exhaustion, poor memory, depression
too much = high blood pressure, anxiety, insomnia
What’s the myelin sheath?
fatty, insulating layer around axon, composed of Schwann cells; protects myelinated axons and speeds the rate of nerve impulse transmission
What conditions must be maintained by Homeostasis?
When Shall I Clean The Utensils
- Water balance - blood volume
- Sugar balance (blood glucose)
- Ion balance - Na, K, H (transport pumps, nervous response, heart function)
- Carbon dioxide levels & pH - too high = acidosis
- Body Temperature
- Urea produced from protein metabolism; toxic and must be eliminated in waste (toxic byproduct from liver)
What mechanisms does homeostasis include?
mechanisms that detect (sensors) & mechanisms that respond to environmental changes to restore normal conditions (effectors)
What’s the synapse? Whats the synaptic cleft?
the junction between two neurons or between a neuron and an effector (muscle or gland)
~ this space is called the synaptic cleft (between the presynaptic & post synaptic neuron)
IMPULSES MUST CROSS SYNAPSE TO REACH NEXT NEURON
What is said about the resting membrane? What is the resting membrane potential of a typical neuron?
it is said to be charged and is called a POLARIZED MEMBRANE
resting membrane potential: -70 millivolts (mv)
Describe the steps involved in carrying a nerve impulse across the synapse.
- the impulse travels to the synaptic terminal
- synaptic vesicles containing neurotransmitters move toward the presynaptic membrane and fuse with it using exocytosis to release neurotransmitters
- neurotransmitters are released into the synaptic cleft
- neurotransmitters bind to receptor proteins (on the postsynaptic membrane) and affect the post-synaptic neuron
~ this triggers sodium channels to open and depolarizes the postsynaptic membrane
~ an action potential is initiated and the impulse continues down neurons - Afterward, an enzyme will break up the neurotransmitter, and its components will be reabsorbed by the presynaptic neuron
What are motor neurons
transmit information from central nervous system to effectors, including muscles, glands, organs
What is the parasympathetic nervous system
- rest/digest response (activated when the body is calm, at rest)
- acts to restore and conserve energy
- slows heart rate, reduces blood pressure, and promotes digestion
- releases acetylcholine
located below and largely behind the cerebrum; involved in the unconscious coordination of posture, reflexes, body movements, and voluntary motor skills
receives info from proprioceptors
cerebellum
What are the functions of the nervous system
- to sense and respond to continuous change within both the body and external environment
- regulates body structures and processes to maintain homeostasis
- can regulate numerous activities simultaneously, including autonomic functions, learning, thought, fine motor coordination
What’s a dendrite
sends messages (electrical impulses) to the soma (nerve cell body)
~ soma: if electrical impulses are large enough, a signal is sent down the axon
What is a nerve impulse?
a series of action potentials
sits at the base of the forebrain; consists of neurons that provide connections between various parts of the brain
thalamus
What is glutamate? What happens when there’s an imbalance?
most abundant in brain; plays a major role in learning, memory, cognition, and mood regulation
too little = trouble concentrating, mental exhaustion, insomnia, low energy
too much = Parkinson’s disease, Alzheimer’s disease, Huntington’s disease (brain cell damage)
What is resting potential?
voltage difference across a nerve cell membrane during the RESTING stage
What’s a node of Ranvier
allows for ions to diffuse in and out of the neuron, propagating electrical signal down the axon
What are neurons?
- structural, function unit of NS
- respond to physical & chemical stimuli
- conduct electrochemical signals
- supported by glial cells (which nourish, remove waste from and defend neurons)
- organized into tissues called nerves
What are sensory neurons
receive stimuli and form a nerve impulse
How does the body regulate temperature when its too cold?
if your body temp is below normal,
- sensors in the skin & brain send messages to the control center
- the control centre sends messages to several effectors
- blood vessels constrict, decreasing heat loss through skin
- hormones are released that lead to an increase in body metabolism , which generates heat
- muscles begin to contract repeatedly, which results in SHIVERING, which increases heat production
- when body temp is back to normal, these responses stop
What is the sympathetic nervous system
- fight or flight response (activated in stressful situations)
- releases norepinephrine which excites target organs to activate a stress response
~ feelings of anxiety, fast heartbeat, and respiration rate
regulates growth, metabolism, and reproduction through the hormones that it produces
pituitary gland
What is the Autonomic Nervous System?
- involuntary
- nerves stimulate or inhibit glands or muscle tissue
- controls heartbeat, peristalsis, and glandular secretions
- further divided into sympathetic and parasympathetic
How does the speed of the action potential differ in myelinated and unmyelinated neurons
- in unmyelinated neurons, conduction of a nerve impulse is continuous
- rather than jumping from one section of an axon to another, action potentials in unmyelinated neurons cause the release of sodium along each adjacent portion of a membrane
- as a result of this step-by-step conduction along the axon, the transmission of an impulse is SLOWER than the saltatory conduction along a myelinated axon
- unmyelinated: 0.5 m/s; myelinated 120 m/s
What is acetylcholine? What happens when there’s an imbalance?
must abundant in muscle; helps with memory and body functions such as muscle contractions to move your muscles
too little = memory issues & muscle disorders
too much = slurred speech, respiratory depression, insomnia, headache, confusion
What is endorphins? What happens when there’s an imbalance?
act as natural painkillers in synapses of the brain; also affects emotional areas of the brain
deficiency linked to an increased risk of alcoholism
What is the PROPAGATION step of generating a nerve impulse?
- for the impulse to be conducted down the axon, it must move to adjacent resting regions, triggering an influx of sodium ions and DEPOLARIZATION as it moves along
- the action potential moves along the axon, creating a wave of DEPOLARIZATION and REPOLARIZATION
How does the body regulate temperature when it is too hot?
if the body temp is too hot,
- signals are sent to control center
- control center directs a response to several effectors, including blood vessels and sweat glands
- the blood vessels dilate, resulting in heat loss through radiation & conduction
- the sweat glands release sweat
- As sweat evaporates from the skin, heat is released from the body
- this continues till body temp returns to normal
What is the hindbrain?
cerebellum, pons, and medulla oblongata
controls body’s vital functions such as respiration and heart rate
What two systems is the Peripheral Nervous System broken down into?
Somatic NS (voluntary)
Autonomic NS (involuntary)
What is the INITIATION step of generating a nerve impulse?
- upon excitation (-50mV/-55mV), sodium channels open causing ions to rush into a small part of the axon, changing the membrane potential to +40 mV
~ this is called DEPOLARIZATION + - at +40 mV, sodium channels close and potassium channels open causing ions to leave the axon REPOLARIZING the membrane
- the potential decreases to -90 mV and potassium channels close
~ this is called HYPERPOLARZATION
How are neurons classified?
By structure - depends on the number of processes that extend from cell body:
1) Multipolar - several dendrites; single axon
2) Bipolar - single main dendrite; single axon
3) Unipolar - dendrite & axon fused
By function - Sensory, integration, motor
What is serotonin? What happens when there’s an imbalance?
regulates temp and sensory perception; involved in mood control
inadequate amounts in the brain synapses are linked to depression
What is the threshold level?
- -50 mV
the minimum level of a stimulus required to produce a response
What’s a neurotransmitter?
chemical messenger secreted by neurons to carry a signal from one neuron to the next
What’s an axon terminal
contains mitochondria & enzymes for making neurotransmitters
largest part of the brain; divided into right and left hemispheres which contain centres for intellect, learning and memory, consciousness, and language (interprets and controls the response to sensory info)
cerebrum
lies just below the thalamus; helps to regular the body’s internal environment as well as certain aspects of behaviour
hypothalamus
What’s the cell body (for a neuron)
processes input from dendrites; site of the cell’s metabolic reactions
What are interneurons
only in central nervous system; act to link sensory and motor neurons
What is action potential?
voltage difference across a nerve cell membrane when the nerve is EXCITED and transmitting an electrical impulse along the axon
What’s a schwann cell
a type of glial cell (support cell); form myelin by wrapping itself around the axon
What is saltatory conduction?
the rapid method by which nerve impulses move down a myelinated axon/neuron with excitation occurring only at nodes of Ranvier
~ they jump from one node of Ranvier to the next due to the myelin sheath
bundle of white matter which joins the left and right hemisphere of the brain; sends messages from one hemisphere to the other
corpus callosum
What is the RECOVERY step of generating a nerve impulse?
- neurons can’t conduct another action potential until the resting membrane potential is restored
- the time required for this repolarization to take place is called the REFRACTORY PERIOD
- the original polarity is restored by the action of the sodium-potassium pump
What’s an axon
transmits action potentials (electrical signals) to axon terminal (terminal buds)
made of Schwann cells which are each separated by a node of Ranvier
sits at the base of the brain stem, connecting the brain with the spinal cord; coordinates many reflexes and automatic bodily functions that maintain homeostasis
medulla oblongata
What is the Reflex Arc? What are the 3 neurons involved?
- a simple connection of neurons that results in a reflex action
~ reflexes are sudden, involuntary responses to certain stimuli (ex. blinking, knee-jerk)
involves: sensory neuron (receptor), interneuron (spinal cord), and motor neuron (triggers muscles)
What is the All or None Response?
- an action potential is triggered when the threshold potential or level is reached
- the strength of the action potential does not change based on the strength of the stimulus
- neurons either fire maximally or not at all
- however, the frequency of impulses does vary, allowing the brain to distinguish between a weak or strong stimulus (the more intense the stimulus, the greater the frequency of impulses sent to the CNS)
What is the Somatic Nervous System?
- under conscious voluntary control
- sensory nerves carry information to the Central Nervous System
- motor nerves carry instructions to skeletal muscles
- controls voluntary movements of skeletal muscles (ex. moving your hand around)
What are the 3 steps to the generation and transmission of nerve impulses?
- Initiation
- Propagation
- Recovery
How is childbirth an example of positive feedback?
- the uterus contracts, forcing the baby’s head or body into the cervix
- the head of the baby presses against the cervix
- this stimulates sensors in the cervix & impulses are sent to the brain, which causes the pituitary gland to release oxytocin
- oxytocin is a hormone that causes muscles in the wall of the uterus to contract
- as labour continues, sensors in the cervix continue to send impulses to the brain which leads to more oxytocin being released
- the release of more oxytocin leads to ever-stronger contractions until birth occurs
What is bio-feedback
information is gathered by the body and sent to the brain to monitor and maintain normal conditions
What are the 3 components of a feedback loop? Describe each.
- Receptor - structures that gather info and detect a stimulus
- Integrator (control center) - receives the info and determines how to act (ex. brain)
- Effector - receives directions from the control center and produces a response that restores the controlled condition (primarily organ & muscles)
What is GABA? What happens when there’s an imbalance?
inhibitory neurotransmitter; helps calm neuronal activity and prevents over-excitation by blocking other messages & controlling the speed at which info travels through the nervous system to maintain balance
too little = anxiety, depression, mood disorders, schizophrenia
too much = autism, high blood pressure, insomnia
How is blood clotting an example of positive feedback?
- after an injury occurs, the affected tissues release chemicals that activate platelets
- the platelets begin the clotting process & release chemicals that stimulate further clotting until the bleeding stops
What do neurons have at rest?
a “membrane potential” which is a form of potential energy created by an electrical charge separation across the membrane
~ the inside (cytoplasmic) side of the membrane is negative relative to the outside (extracellular) side
three layers of tough, elastic tissues that surround and protect the central nervous system
meninges
What are the 2 feedback loops? Describe each.
Negative Feedback Loop - (more common) body’s response leads to a decrease in the stimulus, shutting off the response
Positive Feedback Loop - (more rare) intensifies the stimulus, increasing the response
What are the different lobes of the brain? What are they responsible for?
Occipital Lobe - receives and analyzes visual information; is needed to recognize what is being seen
Parietal Lobe - receives and processes sensory information from the skin
Frontal Lobe - integrates information from other parts of the brain and controls reasoning, critical thinking, memory, and personality
Temporal Lobe - processes visual information as well but mainly focuses on auditory reception (understanding speech & retrieving visual and verbal memories)
above and in front of the medulla oblongata in the brain stem; serves as a relay centre between the neurons of the right and left halves of the cerebellum, cerebrum, and the rest of the brain
pons
What is Homeostasis?
maintenance of a relatively stable internal environment, despite external changes
What is dopamine? What happens when there’s an imbalance?
affects the brain synapses in the control of body movements; is linked to sensations of pleasure such as eating
too little = Parkinson’s disease
too much = schizophrenia
What is nerve signalling?
the communication of nerves
* afferent neurons (PNS detects stimulus; sent to CNS)
* interneurons (CNS brain integrates information)
* efferent neurons (action to the effector; muscle/gland)
How does the body respond to dehydration (loss of water through sweat)?
- sensors in the brain detect less water in blood
- the brain releases antidiuretic hormone (ADH) which signals the kidneys to save water (hence the feeling of thirst to encourage drinking)
How does the body respond to drop in blood glucose levels (due to energy consumption)?
- the pancreas senses the drop in sugar
- it releases a hormone (glucagon) that tells the liver to release stored sugar into the blood, giving more energy
How does the body respond to increased body temperature (due to prolonged muscle activity)?
- heat sensors in the brain & skin detect the rising temperature
- the brain signals blood vessels to widen (vasodilate) and sweat glands to release sweat
How does the body respond to increased carbon dioxide levels (due to rapid breathing & energy use)?
- high CO2 levels are detected by sensors in the blood
- the brain increases the breathing rate to expel more CO2 and bring in more oxygen to support muscles during exercise
