CH8 The Nervous System Flashcards
What are the functions of the Nervous system?
-it detects changes or stimuli inside the body and in the environment. -processes and stores information -initiates responses
What is a stimulus? What is an effector?
A detectable change in the internal or external environment of an organism that produces a response in that organism. An effector is a muscle or gland that causes a response e.g contraction of muscle to move away from heat source.
What are sensory receptors?
They are specialised sensory cells such as pressure sensors in the skin and in complex sense organs like the ear and eye.
Why are sensory receptors described as transducers? What are nervous impulses?
They detect energy in one form and convert it into electrical energy Nervous impulses are electrical impulses that travel along neurons, that initiate a response in an effector.
What is the central nervous system (CNS)?
It comprises the brain and spinal cord and processes information provide by a stimulus.
What is the peripheral nervous system?
Comprises: - the somatic nervous system (pairs of nerves that originate in the brain or the spinal cord, and their branches. These nerves contain the fibres of sensory neurones. Somatic is voluntary actions! - the autonomic nervous system provides unconscious control of the functions of internal organs e.g. Heartbeat- Parasympathetic slowing down of heart rate. Autonomic is involuntary!
Why is the grey matter grey, why is white matter white?
-grey matter is grey because it contains cell bodies/nuclei -white matter is white because it contains Schwann cells which secrete myelin which has lipids-white
What is the advantage of detecting stimuli?
Detecting and responding to stimuli helps to increase an organisms chance of survival.
What is a reflex arc?
A reflex arc is the simplest type of nervous response from a stimulus, which Is the neural pathway taken by nervous impulses in a reflex action.
Give an example of a reflex arc: What is a reflex action?
An example of a reflex arc is a withdrawal reflex e.g placing hand on hot object. A reflex action is a rapid, automatic and involuntary response resulting from nervous impulses of a stimulus. The decision making areas of the brain are not involved.
What is the function of a reflex action? What is different in a knee jerk reflex?
A reflex action has a protective function In a knee jerk reflex, the reflex arc doesnt include a sensory neurone, in which the sensory neurone directly synapses an impulse to the motor neurone.
Explain how a reflex arc works? Use example of withdrawal reflex.
1) Stimulus:** Heat is the stimulus in this case. **2) Receptor-** thermal receptors/pain receptors in the skin detects the heat, and the impulse is sent through the sensory neurone. **3) Sensory neurone:** This sends the impulse to the central nervous system. **4) Relay neurone: This is found in the grey matter, and helps to transmit the impulse to the motor neurone and exits through the ventral root. 5) Motor Neurone: exits via the ventral root and sends the impulse to an effector, which is the skeletal muscle. 6) Effector: Muscle receives impulse. 7) Response: Muscle contracts and hand moves away from heat source.
What neurones in the spinal cord are unmyelinated?
How is a dorsal root ganglion formed?
Relay neurones
The cell boides of the sensory neurons lie together forming a swelling known as a ganglion.
Difference between humans and hydra?
Hydra are organisms that have radial symmetry and their nervous system is a nerve net
Humans are bilaterally symmetrical and have a central nervous sytem (phylum is chordata)
