2.84 Responses/ 2.85 Reflexes

Responses
- A reflex is an action that is performed as a response to a stimulus and without conscious thought eg. moving your hand out of the sun.
- The sensory nerve sends an electrical impulse into the nerves through your arm and up to the Central Nervous System.
- The motor nerve sends the signal to the effector and your body reacts to it.

Reflex actions
- The sensory neuron carries the message from the receptor to the motor neuron which carries the message to the effector to make the interneurons work.
- Reflex actions are rapid and done without thought.

- pain receptor detects a stimulus.
- sensory nerve sends the electrical impulse to the CNS.
- the motor nerve sends the signal to the effector.
- the effector produces a response.

2.83 Central Nervous System

- The central nervous system (CNS) is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies.
- This excludes:sponges and radially symmetric animals such as jellyfish.
- It contains the majority of the nervous system and consists of the brain and the spinal cord.
- Together with the peripheral nervous system, it has a fundamental role in the control of behavior.
- The CNS is contained within the dorsal cavity, with the brain in the cranial cavity and the spinal cord in the spinal cavity.

2.82 Communication

- Nerve impulse is carried along the inside of the nerve from the cell body to the Synaptic Knob where it connects to the muscle - causing it to extend or retract.
- The endocrine gland produces a chemical known as a hormone.
- The Myelin Sheath increases the nerve conduction between components.
- In mammals the axon is surrounded by a Schwann Cell (contains fat)
- Hormones can be proteins or steroids

2.77b Thermoregulation

- Negative feedback loop - method of control and maintaining constant conditions.
- The average body temperature of a human is 37/38 degrees centigrade.
- In order for it to work we have receptors of body temperature - hypothalamus.
- Responds to a stimulus - temp of body and blood.
- Body temperature feeds into the brain and is compared to the theoretical level of control. (37/38degrees).
- If the body temperature needs to be increased of decreased then it is brought about through the action of the effector.

- Input into hypothalamus, stimulates responses in the skin for cooling, sweating + increased blood flow.
- Blood vessels dilate (widen)

2.77a Thermoregulation

- Homeothermic: Same Temperature.
- Homeostasis: Conditions are kept the same or are constant.
- Mammals remain the same body temperature.
- Homeothermic carries out a process called Thermoregulation.
- no matter the increase or decrease of the surrounding temp. the mouses will stay the same.

2.76 Sensitivity

- Sensitivity is the characteristic of the organisms respond to changes in their environment.
- Changes include: Light, temperature, pressure and chemical.
- Organisms are required to have receptors and effectors such as muscles and glands.
Response is used to survive the changes in the environment.