B8 The Nervous System Flashcards
Which 3 main internal conditions require regulation?
- Blood glucose content
- Water content
- Temperature
Which neurones can be found in the CNS?
Relay neurones
What differs a reflex action from other nervous responses?
The signal bypasses the brain, so the response is faster.
How is information transmitted to and from the CNS?
Stimulus → Receptors → Sensory neurone → CNS → Relay neurone → Motor neurone → Effector
What does the myelin sheath do?
Enables electrical impulses to travel quickly and efficiently
What structures connect two neurones?
Synapses
How do electrical impulses travel across the synapse?
Via neurotransmitter chemicals which diffuse across the gap and trigger impulses in the next neurone.
Name one role of a reflex response:
To reduce the chance of harm/injury
Where is the cerebral cortex?
On the outer layer of the brain
What functions are controlled by the cerebral cortex?
Consciousness, intelligence, memory and language
What is the cerebellum responsible for?
Muscle co-ordination
List and explain 3 ways in which neuroscientists study the brain:
- Studying patients with brain damage
- Electrically stimulating the brain
- MRI scans
Via which part of the eye are nervous impulses carried?
Optic nerve
What is the role of the iris?
Controls the diameter of the pupil
What is the name of the tough outer wall of the eye?
Sclera
What is the iris reflex and why is it necessary?
The unconscious contraction of muscles in your iris to let more or less light into the pupil, preventing damage to the eye.
Describe what happens in the eye in dim light:
The radial muscles contract and the circular muscles relax, causing the pupil to dilate.
Explain how the eye focuses on a nearby object:
-Ciliary muscles contract and decrease diameter
-Thus the suspensory ligaments slacken
-Lens becomes more thick and round
-Light is refracted more
-Light focussed onto the retina.
What 2 things are the receptor cells in the retina sensitive to?
Colour and light intensity
What may cause hyperopia?
A misshapen lens or a shortened eyeball
What kind of lens is used to treat myopia?
Concave lens
What is a disadvantage of soft contact lenses over hard ones?
They carry a higher risk of infection.
What does laser eye surgery do?
Change the shape of the cornea by vaporising tissue to correct vision
What complications does laser eye surgery carry?
Worsened vision and infection
What is a risk of replacement lens surgery?
Retinal damage
What part of your brain receives information about body temperature?
Thermoregulatory centre
Where does it receive the information from?
- Receptors in the TRC that detect blood temperature in the brain
- Receptors in the skin that transmit information about skin temperature
What kind of feedback system controls temperature?
Negative feedback system
Explain 3 mechanisms that reduce core body temperature:
- Hairs on the skin lie flat- less air trapped near skin, so less insulation, meaning heat can be transferred to the environment more easily
- Sweat produced- transfers energy to the environment when it evaporates
- Vasodilation- skin capillaries widen- blood flow closer to skin, so energy can be transferred to the environment more easily
How does shivering lead to an increase in body temperature?
Your muscles contract more, requiring more respiration which transfers energy that warms the body.
How can glasses help correct myopia?
The concave lens refracts the light, so that once it passes through the lens, it can be focused on the retina instead of in front of the eye.
Define homeostasis
Regulation of conditions to maintain a constant internal environment
Define stimulus
Change in external environment, usually one that triggers a biological response
Define reflex
Rapid, unconscious response to stimuli
Define accommodation
The reflex action during which the lens changes shape to focus on near and distant objects.
Why does body temperature increase when an organism wakes up from hibernation?
The increase in activity increases the rate of respiration, which in turn transfers thermal energy
