Chapter 5 + 6 Flashcards
Stimulus response model
Stimulus Receptor Transmission of message/Control centre Effector Response
Cell signalling steps
Signal reception
Transduction
Response
Signal transduction
The cascade of events originating outside of the cell leading to a specific cellular response
Signal transduction basis
Amplification
Types of signalling
Autocrine, paracrine, synaptic, endocrine
Autocrine signalling
Secreting cell acts on itself by secreting hormone into extracellular fluid
Paracrine signalling
Secreting cell acts on nearby target cells by secreting hormones into extracellular fluid
Synaptic signalling
Nerve cell releases neurotransmitter into synaptic cleft, stimulating target cell
Endocrine system
System of ductless glands that produce hormones and release them directly into the bloodstream
Signalling molecules
Carry signals or messages from one cell to another
Hormones
Signalling molecule that is produced in an endocrine gland that is release into and transported via the bloodstream to target cells/tissues where it elicits a specific response
Internal environment
The fluid surrounding living cells within a multicellular organism
Examples of internal environment
Lymph, plasma, extracellular fluid, cerebrospinal fluid,
Plasma
The fluid portion of blood in which blood cells are suspended
How is extracellular fluid and plasma separated
Capillaries
Does internal/external environment vary much
Internal not much, external can
Cerebrospinal fluid
Fluid that bathes the brain and spinal cord
What exchanges occur between extracellular fluid and plasma
Passing nutrients, gasses, waste, glucose
What exchanges occur between extracellular fluid and cells
Nutrients, waste, glucose, amino acids
Intracellular fluid is
Cytosol
Homeostasis definition
The maintenance of a relatively stable internal environment within narrow limits
What’s involved in homeostasis
Detecting change, counteracting change
Variables controlled in body
Nutrients, blood volume, temperature, blood pressure, water, oxygen gas, ions, carbon dioxide gas, pH
Nutrients are required for
Energy, repair and growth
Two systems used to communicate and coordinate functions in body
Endocrine and nervous
Difference between hormone and neuron pathways
Speed, blood vs neurons, hormones longer lasting, hormones take longer time to respond to
Similarities with endocrine and nervous
Rely on chemical messengers
Negative feedback system
System of control in which change in a variable is detected and action occurs to produce a change in the opposite direction
Positive feedback
Physiological mechanism that enhances further change in a particular variable that provoked the initial change
Two ways signalling molecules cause cell to elicit a response
Pass through membrane, enter nucleus and bind to receptor
Bind to receptor in membrane, undergoes change in shape, second messengers, they travel along cell and activate other proteins which activates other proteins, until response occurs
cAMP
Cyclic adenosine mono phosphate
Three types of signalling molecules
Peptide, steroid hormones, amino acid derivatives signalling molecules
Hydrophilic
Peptide, amino acid derivative
Lipophilic
Steroid
Lifespan of steroid
Synthesised on demand, leaves by diffusion, long lifespans
Lifespan of protein and amino
Made in advance, stored, short lifespan, exocytosis
Exception
Thyroxine is hydrophobic
cAMP
Second messenger
Core temperature
Temperature of internal cells
pH of enzymes and nerve cells
Generally 7.4
Receptors
Chemical structures, often on the surface of cells that receive signals from hormones, neurons or cytokines
Target cells
Cells with appropriate receptors able to receive particular hormonal or nervous message
Second messenger molecule
Often protein, that acts as an intermediary in the transfer of message e.g. G protein
What happens after hormones have delivered message to target cells
Digested by enzymes
Detecting and responding
Production of signal Detecting of signal Transfer of signal Response Switching off signal
Endocrine signalling
Hormones act on cells
Pheromones
chemicals that, when released by one animal, elicit a response in another animal of the same species; in particular, act as a sex attractant for mating in many insect species
Pheromones are…
specific
Central nervous system (CNS)
in vertebrates, the brain and spinal cord.
Peripheral Nervous System (PNS)
in vertebrates, all nerve cells that in whole or part lie outside the brain and spinal cord.
Two divisions of the PNS
the sensory and motor divisions.
Sensory (afferent) division
informs the central nervous system about the internal environment, via visceral sensory neurons, and about the external environment, via somatic sensory neuron.
Motor (efferent) division
also called efferent division; part of nervous system that transmits nervous impulses from the central nervous system to muscles and glands.
The sensory division is made up of the
somatic sensory neurons and visceral neurons.
Somatic sensory neurons - neurons that carry information to the central nervous system from the external environment via the sense. visceral sensory neurons: transmit information to the central nervous system from the internal environment of the body.
Somatic sensory neurons
neurons that carry information to the central nervous system from the external environment via the sense. visceral sensory neurons: transmit information to the central nervous system from the internal environment of the body.
Visceral sensory neurons
transmit information to the central nervous system from the internal environment of the body.
What does the motor division do
transmits impulses away from the CNS to effector organs.
Effector organs - organs that respond to stimuli from the nervous system.
Effector organs
organs that respond to stimuli from the nervous system.
Somatic nervous system
also called voluntary nervous system; in vertebrates, group of nerves transmitting signals away from the brain and spinal cord to skeletal muscles.
Autonomic nervous system
also called involuntary nervous system; in vertebrates, nerves that transmit messages away from the brain and spinal cord to smooth (involuntary) muscle, heart and various glands. Also called involuntary nervous system.
The autonomic system has two parts
sympathetic and parasympathetic nervous system.
Sympathetic nervous system
part of the autonomic nervous system that supports physical activity of the body.
Parasympathetic nervous system
calms body down, maintains homeostasis, reverses effects
Cell body
that part of a neuron that contains the nucleus.
Axon
extension of a nerve cell along which impulses are transmitted away from that cell.
Axons vary in length from…
a few millimetres to over a metre.
Dendrites
branched extensions of nerve cell that transmit impulses to that cell.
Myelin Sheath
fatty substance forming an outer covering around some axon. For speed and protection.
Nerve
bundle of parallel axon and dendrite fibres surrounded by connective tissue.
Three types of neurons
affector, effector and connecting neurons.
Affector neurons
also called sensory neurons; type of nerve cell that transmits information about changes in external or internal conditions to the central nervous system.
Effector neurons
also called motor neurons; type of nerve cell that transmits information from the central nervous system to muscle cells or glands.
Connecting neurons
also called interneurons; type of nerve cell, located in the central nervous system, that links sensory and effector neurons.
Reflex arc
stimulus, receptor/affector, CNS (interneurons), effector, response
A nerve that is not responding to a stimulus is said to be
‘resting’ or ‘at rest’
Nerve impulse
change that occurs in the electrical charge along a neuron membrane in response to a particular stimulus.
Transmitter substance
compounds produced and released at the ends of axons e.g. acetylcholin
Synapse
the junction between two neurons
Neurotransmitter
chemical released by a neuron axon into the synaptic cleft between it and the target cell; stimulates or inhibits the target cell.
Neurohormones
hormones released by the axon end of a neuron into the bloodstream.
Pituitary
endocrine gland attached to the hypothalamus that influences the production of thyroxine by the thyroid.
Antitoxins
protein produced by animals in response to toxin
Anti-venom
chemical that acts to neutralise the effect of a venom.
Meninges
membranous tissue surrounding the brain and spinal cord and separated from them by a thin layer of fluid.
Thalamus
sensory information
Hypothalamus
regulating body, hormones
Venom vs toxin
venom is fluid injected by other animals, toxins are chemicals that are poisonous to organism
Osmoregulation
maintenance of constant internal salt and water concentrations in internal fluids (homeostasis) in spite of different concentrations in the external environment.
What would happen if cells couldn’t communicate
couldn’t have a stable environment
Nerves
long pieces of tissue that transmit electrical messages extremely rapidly between tissues
Action potential
when the axon hillock generates its own electrical transmission when the sum of the signals is sufficiently excitatory
Process of action potential
- The action potential is propagated rapidly through the axon until the synaptic terminal, where it transmits its signal to the next neuron or to another tissue. The myelin sheath makes the action potential travel faster along the axon.
- excited, causes sodium pump send in sodium which increases voltage, sodium closes, then potassium pump sends ion which decreases voltage, potassium pump closes causing action potential to return to normal,
Na/K pump
pump that transports Na+ ions out go the axon and K+ ions into the axon
Na/K pump is made of a
protein
What does Na/K pump do
ensures there is no build up of Na+ ions inside the axon and K+ ions outside the cell by pumping them back where they came from
When extra Na+ ions are inside axon
they travel along the axon to the next segment of the axon, increasing the voltage there. Here there are NAVs that have not yet been activated. The increase in voltage causes these NaVs to open, leading to an action potential at that segment of axon. This causes an action potential in the next segment, and the next and so on. This is how the action potential is propagated along the axon.
All action potentials are…
the same (either on or off)
What is it called when all action potentials are the same
all or nothing effect
Only thing that differs in action potential
frequency
What happens to Na when K is opened
inactivated, can’t open
Hyper-polarised
when it is just lower than normal
Hyper-polarised definition
takes more stimulation than usual to propagate another action potential
Absolute refractory period
just after Na channels close
Relative refractory period
when voltage is lower than normal
Where do neurotransmitters bind to next neuron
protein receptors in dendrite
When reaches axon terminal
calcium channels activated, so Ca2+ ions enter act as vesicles of neurotransmitters (signalling molecules)
Ca2+ is involved in release of
neurotransmitters
When neurotransmitter binds
causes the voltage to increase, (excitatory signal), or decrease (inhibitory signal)
What happens to neurotransmitter
immediately re-uptaken by synaptic terminal or digested by enzyme
What happens if neurotransmitter not re-uptaken or digested
re-stimulates neuron,
Auxin
growth and elongation, apical dominance (lateral buds don’t develop while shoot is growing)
Tropism
growth
Positive/negative tropism
positive grows towards, negative grows away
Geotropism
gravity
Phototropism
light
Auxin goes away from
light
Who did the coleoptile experiment for auxin
Darwin
Cytokinins
growth and division of plant cells
Gibberellins
growth and development of plant cells, seed germination
Abscisic acid
inhibits plant growth and development, closure of stomata to prevent excessive loss of water
Ethylene
ripening of fruit, abscission of leaves
Florigen
controls flowering
Important to remember about florigen
not considered a hormone
Cell junctions
junctions that allow molecules to readily pass between adjacent cells without crossing membranes
Cell-cell recognition
communication by interaction between molecules protruding from their surfaces
