Homeostasis (Unit 2 - Topic 1) Flashcards
Anabolism
= Metabolic process that builds molecules the body needs.
eg. amino acids becoming polypeptides (proteins).
Catabolism
= Metabolic process that breaks down large molecules into smaller molecules.
eg. proteins becoming amino acids
Homeostasis
= a stimulus-response model in which changes in the condition of the external or internal environment is detected and appropriate responses occur via negative feedback.
= is the tendency to resist change in order to maintain a stable, relatively constant internal environment
Effectors
= Muscles - contract in response to neural stimuli.
= Glands - produce secretions
Negative Feedback loop
= counteracts changes of various properties from their target values, known as set points
= the typical method of achieving homeostasis
= serves to reduce an excessive response and keep a variable within the normal range.
= eg. temperature regulation and control of blood glucose.
Sensory receptors
= detects stimuli
= can be classified by the type of stimulus
chemoreceptor
= a sensory receptor that responds to chemical stimuli
eg. Taste buds and food
eg. Carbon-dioxide receptors in lungs
thermoreceptor
= a sensory receptor that responds to temperature stimuli.
eg. Thermoreceptors allow the hypothalamus to react to a predicted change in core body temperature in response to changing environmental conditions.
mechanoreceptor
= a sensory receptor that responds to mechanical stress or strain
photoreceptor
= a sensory receptor that responds to visible light
nocireceptor
= a sensory receptor that responds to damaging or potentially damaging stimuli by sending “possible threat” signals = pain
metabolism
= all of the chemical reactions involved in sustaining life
= is either catabolic or anabolic
sensory neuron
= responsible for converting external stimuli from the environment into corresponding internal stimuli
= activated by physical stimuli (such as visible light, sound, heat, physical contact, etc.) or by chemical stimuli (such as smell and taste).
= pseudounipolar - they have an axon that branches into two extensions—one connected to dendrites that receive sensory information and another that transmits this information to the spinal cord
motor neuron
= neurons located in the central nervous system, and they project their axons outside of the CNS to directly or indirectly control muscles
= multipolar, meaning each cell contains a single axon and multiple dendrites
= the most common type of neuron.
axon
= a tube-like structure that carries an electrical impulse from the cell body (or from another cell’s dendrites) to the structures at opposite end of the neuron—axon terminals, which can then pass the impulse to another neuron
dendrite
= branch-like structures extending away from the cell body
= their job is to receive messages from other neurons and allow those messages to travel to the cell body.
soma
= Like other cells, each neuron has a cell body (or soma) that contains a nucleus, smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria, and other cellular components
myelin sheath
= external coating functions as insulation to minimise dissipation of the electrical signal as it travels down the axon
= made from myelin, a fatty material that wraps around the axon
node of Ranvier
= Periodic gaps in the myelin sheath where the signal is recharged as it moves along the axon
synapse
= the chemical junction between the axon terminals of one neuron and the dendrites of the next
= It is this gap where specialized chemical interactions can occur
action potential
= A short-term change in the electrical potential that travels along a cell, such as a nerve or muscle fiber, and allows nerves to communicate
= An action potential occurs when an electrical signal disrupts the original balance of Na+ and K+ within a cell membrane, briefly depolarizing the concentrations of each
neural impulse
= The signal transmitted along a nerve fiber, either in response to a stimulus (such as touch, pain, or heat), or as an instruction from the brain (such as causing a muscle to contract)
the stages of an action potential
= 1. Depolarization: A stimulus starts the depolarization of the membrane
= 2. Repolarisation: Once the electric gradient has reached the threshold of excitement, the repolarisation begins
= 3. Refractory Phase: The refractory phase takes place over a short period of time after the depolarization stage
neurotransmitters
= a chemical released from a neuron ending in response to a nerve impulse that interacts specifically with receptors on a responding cell
receptors
= a specialised structure that can detect a specific stimulus and initiate an action potential
synaptic cleft
= the physical space between two neurons
= the space that separates a neuron and its target cell at a chemical synapse
postsynaptic neurones
= a neuron to the cell body or dendrite of which an electrical impulse is transmitted across a synaptic cleft by the release of a chemical neurotransmitter from the axon terminal of a presynaptic neuron
presynaptic neurones
= a neuron (nerve cell) that fires the neurotransmitter as a result of an action potential entering its axon terminal
signal transduction
also known as cell signaling
= the transmission of molecular signals from a cell’s exterior to its interior. Signals received by cells must be transmitted effectively into the cell to ensure an appropriate response. This step is initiated by cell-surface receptors.
