Nerves and hormones Flashcards
What is the nervous system?
A group of organs that work together to enable us to react to our surroundings and coordinate our behaviour
Give five types of receptor cells (cells that detect stimuli), what part of the body they would be in, and the stimulus (change in environment) they detect
Eyes - light
Ears - sound; changes in position and allow balance
Tongue and nose - detect chemicals and allow taste and smell
Skin - touch, pressure, pain and temperature changes
How does information from receptors get to the brain?
What then happens?
It passes along nerve cells (neurones) in nerves to the brain
The brain coordinates a response
What are reflex actions? What types of neurones do they involve?
Automatic and rapid actions that don’t require conscious thought
Sensory, relay and motor neurones
Define a synapse
A junction or gap between two neurones, over which a chemical (neurotransmitter) is secreted that causes an impulse to be sent
Define an effector
Either a muscle or gland that brings about the response to stimulus
Step 1 of a simple reflex action
Impulses from a receptor pass along a sensory neurone to the central nervous system (CNS), until it causes a chemical to be released to send an impulse along a relay neurone in the CNS
Step 2 of a simple reflex action
A chemical is released at the synapse between the relay neurone and a motor neurone, causing an impulse to be sent to the effector
Step 3 of a simple reflex action
Muscle would then respond by contracting; a gland by secreting (releasing) chemical substances
Give four examples of four internally controlled conditions and why
Water content - leaves the body via the lungs with exhalation and via the skin with sweating, and excess is lost via the kidneys in urination
Ion content - lost via sweating and urination
Temperature - maintain optimum temperature for enzymes
Blood sugar - to provide cells with constant energy supply
What do hormones do, where do they come from and how are they transported to their target organs?
They coordinate many bodily processes, especially the functions of many organs and cells
Secreted by glands
Transported by bloodstream
Describe how hormones control the menstrual cycle of a woman
FSH (follicle stimulating hormone), secreted by the pituitary gland, causes eggs to mature in the ovaries, and stimulates the ovaries to produce hormones including oestrogen
LH (luteinising hormone) stimulates the release of eggs
Oestrogen inhibits the further production of FSH
Hormones also control the thickening of the womb lining
How are hormones used in oral contraceptives?
They contain oestrogen and/or progesterone to inhibit FSH production, so that no eggs can mature
What did the first birth-control pills contain that resulted in women suffering significant side effects? How has this now been rectified?
High levels of oestrogen
Less oestrogen and more progesterone, or only progesterone is now used, which leads to fewer side effects
How are hormones used in helping women who are infertile due to a lack of FSH to have a baby? Example: In Vitro Fertilisation
FSH and LH are given to stimulate the production of eggs, which are collected and then fertilised by the father’s sperm
They then grow into embryos, one or two of which are implanted into the uterus at an early stage
