Communication & Homeostasis Flashcards
What’s the role of receptors in homeostasis?
to detect changes in stimulus involved in physiological processes.
Why are receptors described as transducers?
they convert a stimulus into a nerve impulse/action potential.
What is a Shwann cell?
the cell which produces the sleeve of protein and fatty material which covers some neurones.
What is the refractory period?
the period of time when a neurone is unable to repeat an action potential.
Describe how voltage-gated channels and the movement of sodium ions prevent the generation of an action potential during the refractory period.
The voltage-gated sodium channels are closed, preventing movement of sodium ions into the axon.
This stops the generation of an action potential.
Give two reasons why a refractory period should follow an action potential.
it ensures action potentials are:
- unidirectional
- occur as discrete impulses
‘What is the all-or-nothing’ response in terms of neurone action potentials?
- Neurones always generate action potentials of the same size, no matter how large the stimulus.
- The stimulus must also reach a minimum threshold or no action potential is generated.
What is saltatory conduction?
the method of conduction in myelinated axons that involves action potentials jumping from one node of Ranvier to the next.
List three factors that affect the speed of conduction along an axon.
- myelination
- axon diameter
- temperature
Which neurotransmitter is found in cholinergic synapses?
ACh
Name the two categories synapses can be placed in, based on how they affect the likelihood of an action potential occurring.
excitatory and inhibitory synapses
What effect do inhibitory synapses have on the postsynaptic membrane?
hyperpolarisation
What is summation?
the process in which more than one impulse is needed to generate an action potential at a synapse.
What is temporal summation?
the process by which an action potential is generated from a single presynaptic neurone releasing neurotransmitters a number of times.
What is spatial summation?
the process by which an action potential is generated from multiple presynaptic neurones releasing neurotransmitters.
What is resting potential?
the voltage across a neurone membrane when not stimulated by an action potential.
Describe how a resting potential is established.
- sodium-potassium pump.
- 3 Na+ ions are transported out of the cell, and 2 K+ ions are transported in.
- active transport.
- electrochemical gradient is established (inside of cell is more negative than the outside).
What term is used to describe communication between adjacent cells or cells at a distance?
cell signalling.
What two systems are used in animals to coordinate responses to changes in the environment?
- the endocrine system.
- the nervous system.
Comment on the speed, duration and distribution of responses produced by hormones.
Hormones usually produce a response that is long-lasting, slow, and widespread.
Comment on the speed, duration and distribution of responses produced by nerve impulses.
Nerve impulses produce responses that are usually localised, short-lived and rapid.
What is negative feedback?
the type of homeostatic control in which the response to a stimulus restores a factor to its original set point.
What is positive feedback?
the type of homeostatic control in which the response to a stimulus causes a factor to deviate further from its original set point.
What is a receptor?
A cell or protein that detects one specific type of stimulus.
What is an effector?
A part of the body, often a muscle or gland, that produces a response to a stimulus.
What is meant by the term “ectotherm”?
An animal which depends on the environment to regulate its internal body temperature.
What are (2) examples of behavioural responses ectotherms use to control their internal temperature?
- sun basking
- shade seeking
What is meant by the term “endotherm”?
An animal that maintains a stable internal body temperature regardless of the external temperature by generating heat through metabolic processes.
In endotherms, temperature receptors are located in which two parts of the body?
- the skin
- the hypothalamus
In endotherms, which part of the brain is involved in thermoregulation?
the hypothalamus.
What is seen in endotherms in response to a rise in core body temperature?
- vasodilation
- sweating
- relaxing hair erector muscles (to lower hair)
What is seen in endotherms in response to a fall in core body temperature?
- vasoconstriction
- shivering
- contracting hair erector muscles (to raise hairs)
Where in the body are the Islets of Langerhans found?
the pancreas.
What is the function of the Islets of Langerhans?
to produce and secrete hormones.
Which cells (and where) is glucagon produced in?
alpha cells in the Islets of Langerhans.
Which cells (and where) produce insulin?
beta cells in the Islets of Langerhans.
Define glycogenesis.
the conversion of glucose to glycogen.
Define glycogenolysis.
the conversion of glycogen to glucose.
Define gluconeogenesis.
the conversion of non-carbohydrate molecules to glucose.
Describe how insulin binding to receptors controls the uptake of glucose into cells.
- insulin has a specific tertiary structure which allows it to bind to insulin receptors on the surfaces of target cells.
- binding of insulin regulates the inclusion of channel/transport proteins in the cell-surface membranes of the target cells.
- glucose enters through the channel/transport proteins.
What type of diabetes arises when the body becomes unable to produce insulin?
type 1 diabetes.
How does Type 2 diabetes arise?
Type 2 diabetes can arise from glycoprotein receptors being lost or being less responsive to insulin, or from insufficient insulin production in the pancreas.
