Topic 1: Nerves & Hormones

Question 1

CONTROL SYSTEMS

• In mammals the coordination of activities such as detecting and responding to environmental changes is carried out using the nervous and endocrine (hormonal) systems.
• Hormones are chemicals that travel through the blood stream and control growth, metabolism, sexual function, reproduction and mood.

Answer 1

NERVOUS SYSTEM

• The nervous system uses receptors to gather information about the function of the body and the external environment.
• It then provides fast response to that information by acting on glands or muscles (effectors).
• Glands synthesis hormones
• Vertebrate nervous system consists of the;
• Central Nervous System (spinal chord and brain)
• Peripheral Nervous System

Question 2

STEPS WITHIN THE NS

• 1. Sensory neurones detect the change (touch sensors).
• 2. This change gets turn d into an electrical impulse and travels to the spinal chord.
• 3. The spinal chord either sends the message to the brain for interpreting or acts straight away.
• 4. Motor neurones get sent out and you act (reflex).

Answer 2

RECEPTORS

• Sensory nerve endings receive information then conduct a process to generate nerve impulses which are transmitted to the brain for interpreting.
• Sensory receptors react to the physical stimulus in the environment including
• Taste- gustatory receptors
• Odor/Smell- olfactory receptors
• Vision- photoreceptors

Question 3

NERVE CELLS;

• Your brain contains an estimated 100 billion nerve cells.
• Specialised for carrying signals from one location in the body to another.
• Each neurone May communicate with thousands of others forming networks.

Answer 3

STRUCTURE OF NERVE CELLS

• Nerve impulses are received by the dendrites, travel down the branches to the nerve cell body and then are carried all the way along the axon.
• Nerve Cell Body; contains nucleus and organelles
• Dendrites; branching off the nerve cell body, acting like tiny antennae, picking up signals from other cells
• Axon; At the opposite end of the nerve cell body, it is a long thin fibre with branches at the end
• Synapse; the site of transmission of electric nerve impulses between two nerve cells
• Neurotransmitters; chemicals which allow the transmission of signals from one neurone to the next across the synapse

Question 4

TYPES OF NERVE CELLS

• Sensory Neurones; Nerve cells responsible for converting external stimuli from the environment into electrical nerve impulses (from sensory organs to CNS).
• Interneurons; Intermediary in passing signals and information, read impulses received from SN (found in the CNS).
• Motor Neurones; Transmit impulses from spinal chord to control muscle or glands (from CNS, stimulate effectors).

Answer 4

ENDOCRINE SYSTEM

• The endocrine System is made up of a number of glands throughout the body.
• Glands secrete hormones directly into the bloodstream.
• The action of the system is slower than the nervous system but has a more widespread and long-lasting action.

Question 5

HORMONES

• Chemical messages produced by the endocrine glands.
• Thyroxine; produced by thyroid glands, acts on most tissues and effects metabolism
• Insulin; produced by the pancreas, acts on muscle, liver and fat and promotes glucose creation
• Adrenaline; produced by the adrenal gland, acts on muscles and blood and diamanté’s blood vessels

Answer 5

STEROID HORMONES

• Testostrone or Estrogen
• Lipids (fat)
• Hydrophobic meaning the pass through the plasma membrane into cells.
• Receptors for steroid hormones are located inside the cell.

PEPTIDE HORMONES

• Insulin
• Short chains of amino acids.
• Hydrophyllic meaning they can’t pass easily through the cell.
• Receptors are on the surface of the cell.

Question 6

RESPONDING TO CHANGE

• In order to survive and reproduce, an organism must detect and respond to change in its environment.
• They do so using sensory organs which in turn send messages to the CNS via sensory neurones.
• When the message reaches the CNS it may cause on automatic response (reflex) or it may be slower and involve the brain.
• Effector organs are always muscles or glands. In feedback mechanisms the transmission of the message can be by nerve or hormone.

Answer 6

STIMULUS RESPONSE MODEL

• The order of the process is important.
  1. Stimulus; a detectable change in the environment
  2. Receptor; the detector of the change referring to our sensors
  3. Message; the method of message transmission (Nervous, hormonal or both)
  4. Effectors; muscles or gal do
  5. Response; the change in conditions

Question 7

NEGATIVE FEEDBACK

• Negative feedback is when the response reverses the stimulus.
• Negative feedback is a process that maintains control and keeps body systems operating within set limitations.
• This is called homeostasis.
• Examples include temperature control, blood glucose levels, hormone levels, blood pH, blood CO2, and blood water levels.

Answer 7

REFLEX ARC

• The reflex arc is an example of an instant response and involves only nervous messages.
• The stimulus is from internal or external changes.
• Stimulus is detected by receptors.
• Only involves nerves and muscles.
• Eletrical message moves along the sensory nerve to the CNS and then via intermediate nerves to a motor neurone.
• The eletrical message then moves to the effector muscles and the muscles contract leading to a response .
• The brain is not involved in the initial response.

Question 8

TEMPERATURE CONTROL
TOO HOT
- Stimulus; too hot
- Receptor; thermoreceptors in the skin and hypothalamus
- Message; both nerves and hormones
- Effectors; glands (swear, adrenal and thyroid)
- Response; thyroxine/adrenaline levels drop and sweating begins

Answer 8

TOO COLD

• Stimulus; too cold
• Receptor; thermoreceptors in the skin and hypothalamus
• Message; both nerves and hormones
• Effectors; glands (swear, adrenal and thyroid) & muscles
• Response; thyroxine/adrenaline levels increase and muscles shiver