Chapter 10 - The Nervous System and the Eye Flashcards
The nervous system and the endocrine system work together to….
Maintain the internal environment in the human body (aka homeostasis)
What does the nervous system use to coordinate activities in the body?
Nerve impulses
What does the endocrine system depend on for effective coordination of activities?
Hormones
Homeostasis is carried out by the nervous system, which involves what stages?
Stimulus –> Receptor –> Reflex/Control centre –> Effector –> Response
What does the nervous system in humans do?
Regulates bodily functions and activities and how we react to the surroundings
What is the stimulus?
- Homeostatic control is always triggered by a stimulus
- It is a change in the environment that causes an organism to react
What is the receptor?
The receptor in sense organ detects the stimulus and sends nerve impulses down the sensory neurone and relay neurone to reach the control centre
What is the reflex centre?
- The brain and the spinal cord which act as a coordination centre
- After processing info, the brain or the spinal cord sends nerve impulses down the relay neurone and motor neurone to the effector (to ‘instruct’ us on how to react to the stimulus)
What is the effector?
- The effector brings about a response
- The effector is a muscle (In endocrine system, effector is an endocrine gland)
What is a response?
- A response is the organism’s reaction to a stimulus
- The muscles contract (n endocrine system, a gland secreted hormones)
What is the ability to respond to a stimulus known as?
Sensitivity or irritability (e.g. touching a hot object [stimulus], and moving hand away [response to stimulus])
What is the nervous system made up of?
1) Central nervous system
- Brain
- Spinal cord
2) Peripheral nervous system
- Cranial nerves
- Spinal nerves
- Sense organs
What are neurones?
Nervous tissue have nerve cells aka neurones. Bundles of neruones are called nerves
Describe the sensory neurone
Structure: Has a circular cell body, with a nucleus, cytoplasm, cell membrane, organelles, a long nerve fibre towards the receptor and a short one towards relay neurones
Function: Transmits nerve impulses from receptors to CNS
What is a nerve fibre?
A strand of cytoplasm extending from the cell body
Describe the relay neurone
Structure: Intermediate neurone within the CNS
Function: Transmits nerve impulses from the sensory neurone to the motor neurone
Describe the motor neurone
Structure: Irregular shape of cell body containing nucleus, cytoplasm, cell membrane, organelles
Function: Transmits nerve impulses from CNS to effector to produce a response
What is a reflex arc?
The shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action
Describe the pathway of a reflex arc
Stimulus → Receptors → Sensory Neurone → CNS (Relay Neurone) → Motor Neurone → Effector → Response
What is a synapse?
The junction between 2 neurones where nerve impulses are not able to cross from one neurone to the next directly (due to the tiny spaces between)
What happens when a nerve impulse reaches one end of a neuron?
It stimulates the release of chemicals into the synapse that diffuse across the tiny space where they trigger the formation of a new nerve impulse in the next neurone
What do nerve impulses not carry?
They do not carry sensations (e.g. pain, cold). Nerve impulses are just electrical impulses that travel down the neurones within a fraction of a second
What are sensations?
When holding ice, the temperature receptors n skin are stimulated and nerve impulses produced are transmitted to the brain. The brain interprets the nerve impulses and that is the sensation of coldness
(Receptor –> Sensory neurone –> Relay neurone in SC –> Brain)
What are voluntary actions?
When raising a hand in class, nerve impulses are produced in the brain, transmitted by a relay neurone from the brain, down the spinal cord. In spinal cord, nerve impulses are transmitted to the motor neurone, to the effector muscles in the arm. The muscles contract and arm is raised
(Brain –> Relay neurone in SC –> Motor neurone –> Effector)