Cell Signalling

Question 1

Define Homeostasis

Answer 1

Cells need to maintain a relatively stable internal environment, so that normal cellular functions can be performed am the cell can perform at optimum efficiency
This is called homeostasis

Question 2

Define a stimulus

Answer 2

a detectable change in the internal or external environment

Question 3

What two interacting systems control homeostasis in animal cells?

Answer 3

endocrine and nervous

Question 4

define the endocrine system

Answer 4

the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things

Question 5

define the nervous system

Answer 5

the network of nerve cells and fibres which transmits nerve impulses between parts of the body

Question 6

What controls homeostasis in plant cells?

Answer 6

plant regulators

Question 7

define chemical messengers

Answer 7

a direct result of a change in the cell environment

cellular responses are due to the specific characteristic of the chemical messengers involved

Question 8

Outline the steps in the Stimulus response model

Answer 8

Stimulus -> receptor->(messages sent)->Control centre->(messages sent)->effector->response

Question 9

What is Negative feedback?

Answer 9

Common. forms a looped system that restores the condition to a steady state and has a stabilising effect
constant stabilising effect keeps extremes in balance

Question 10

What is positive feedback?

Answer 10

Rare. results in the escalation of a response to a stimulus, causing system instability
they amplify a physiological response in order to achieve a particular result
A positive feedback loop will end when a natural resolution is reached

Question 11

What are some examples of negative feedback?

Answer 11

sweating and shivering to stabilise body temperature,

Question 12

What is an example of positive feedback

Answer 12

labour

Question 13

which system is responsible for the production of chemical messengers?

Answer 13

the endocrine system

Question 14

The chemical messengers produced in the endocrine system are called what?

Answer 14

hormones

Question 15

Define hormones

Answer 15

organic molecules produced an secreted by one type of cell and travel via extracellular fluid (usually blood) and act on Specific Target Cells causing profound effects

Question 16

Why do chemical messengers only act on target cells?

Answer 16

Only target cells possess receptors for specific chemical messengers

Question 17

What are the three main groups of hormones?

Answer 17

Proteins/Peptide: (insulin, adrenalin)
Steroids (lipids): (testosterone, oestrogen)
Amino Acid derivatives: (thyroxin)

Question 18

Outline Protein based hormones

Answer 18

protein-based hormones are water soluble, meaning thy cannot cross the lipid-layer of cells
protein-based hormones must activate receptors on the surface of the cell membrane to start the cellular response

Question 19

Outline the signal transduction pathway

Answer 19

when a signalling molecule joins a receptor a set of chemical reactions (or cascade) occurs, known as a transduction pathway
the end result is a response that will have an effect on the stimuli (that generated the signal molecule that started the process)
Reception -> Transduction -> Response

Question 20

Outline Steroid-signalling molecules

Answer 20

Lipid soluble, steroid molecules pass through the cell membrane and bind to a receptor protein found only in target cells. the hormone receptor complex then enters the nucleus and binds to particular sites on the cell DNA
This stimulates Protein Synthesis

Question 21

What are the two main sections of the nervous sytem?

Answer 21

Central Nervous System (Brain + Spine)

Peripheral Nervous System

Question 22

What are the three types of neurons?

Answer 22

sensory, intermediate and motor

Question 23

What happens when neurons are stimulated?

Answer 23

when stimulated, neurons produce electrical impulses that are transmitted along the axon.
These impulses are transmitted across junctions called synapses

Question 24

Outline a chemical synapse

Answer 24

one neuron releases neurotransmitter molecules into a small space (the synaptic cleft) that is adjacent to another neuron. The neurotransmitters are kept within small sacs called vesicles, and are released into the synaptic cleft by exocytosis

Question 25

define a tropism

Answer 25

a stimuli that causes a reaction in plants

controlled by plant reulators

Question 26

what are some examples of tropisms?

Answer 26

phototropism: light
geotropism: gravity
hydrotropism: water
thigmotropism: touch

Question 27

define auxins

Answer 27

a group of regulators that effect cell growth in a plant

Question 28

what are neurohormones?

Answer 28

hormones produced and released by specialise neurosecretory cells which function as both nerve cells and endocrine cells

Question 29

What are the three types of cell signalling?

Answer 29

Endocrine: hormones that are carried by the circulatory system tot eh target cells
Paracrine: signals released from a cell that act on target cells nearby
Autocrine: cells produce and react to their own signals