Chapter 14: Coordination and response Flashcards
What makes up the mammalian nervous system?
The central nervous system (CNS): consists of the brain and spinal cord
The peripheral nervous system (PNS): consists of the nerves outside of the brain and spinal cord
What is the role of the nervous system?
Coordinate electrical impulses travelling through the nervous system, and regulate body functions
What are the structures of sensory, relay, and motor neurones?
Sensory: cell body in the middle, long dendrites and long axons branching out
Relay/interneurone: short dendrites and short axons
Motor: short dendrites, long axon
What is a simple reflex arc?
A series of neurones (sensory neurone, relay/interneurone, motor neurone) that transmit electrical impulses from a receptor to an effector
Define ‘reflex action’
A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors, muscles and glands
Define ‘synapse’
A junction between 2 neurones
What is the structure of a synapse?
Synaptic vesicles, which contain neurotransmitters, are present on the axon terminal. The gap between the axon and the dendrite is known as the synaptic gap, and receptor proteins are present on the membrane of the dendrite
What happens at a synapse?
A nerve impulse arrives at the axon terminal, stimulating the release of neurotransmitters from the vesicles into the synaptic gap. The neurotransmitters diffuse across the synapse and bind with the receptor proteins on the membrane of the dendrite, stimulating it to generate a nerve impulse
What is the importance of synapses?
They ensure that impulses travel in one direction only
Define ‘sense organ’ with examples
Groups of receptor cells responding to specific stimuli, such as light, sound, touch, temperature and chemicals
What is the structure of the eye? (7)
The cornea is the outermost layer, the iris is the little flap thing, the pupil is the inside of the bulge, the lens is the clear thing behind the iris, the retina is at the layer at the back behind the cornea, the optic nerve is the little tail, and the blind spot is at the beginning of the optic nerve
What are the functions of the cornea, iris, lens, retina, and optic nerve?
Cornea: refracts light
Iris: controls how much light enters the pupil
Lens: focuses light onto the retina
Retina: contains light receptors, some sensitive to light of different colours
Optic nerve: carries impulses to the brain
How does the pupil reflex work?
As light intensity changes, the iris can alter the size of the pupil to allow more or less light to enter. The iris contains muscles, circular muscles, which are arranged in circles around the pupil, and radial muscles, which run outwards from the edge of the pupil. These muscles are antagonistic, they work together to control an action and have opposite effects. In dim light, the radial muscles contract, increasing the size of the pupil and allowing more light to enter. In bright light, the circular muscles contract, decreasing the pupil size and allowing less light to enter.
How does accommodation to view near and distant objects work?
In order to form a clear image of an object, light rays must be focused sharply onto the retina. Accommodation is the eye’s ability to focus objects at varying distances onto the retina, which is done by changing the thickness of the elastic lens by the actions of the ciliary body. When looking at near objects, the ciliary muscle contracts and the suspensory ligaments relax, causing the lens to get thicker and greatly refract the light rays. When looking at distant objects, the ciliary muscle relaxes and the suspensory ligaments contract, causing the lens to get thinner and refract light rays less.
How are rods and cones distributed in the retina?
Cone cells are packed tightly in the fovea, and rod cells are less tightly packed and present further out on the retina, near the periphery
What are the functions of rods and cones?
Rods: responsible for vision in dim light, do not detect colour
Cones: able to distinguish between the different colours of light, red, green, and blue light, but only function in bright light
Where is the fovea, and what is its function?
The little dent thing near the back of the eye, where light is focused when looking directly at an object
Define ‘hormone’
A chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
What, and where, are the endocrine glands, and what do they secrete?
Adrenal glands: located just above the kidneys, secrete adrenaline
Pancreas: that feather-looking thing between the kidneys 💀, secretes insulin and glucagon
Testes: down there, secrete testosterone
Ovaries: also down there, secrete oestrogen
Define ‘adrenaline’ and what are its effects?
The hormone secreted in ‘fight or flight’ situations, causes increased heart and breathing rate, increased pupil diameter
What is the role of adrenaline in the control of metabolic activity?
Increases blood glucose concentration and heart rate
What are the differences between nervous and hormonal control?
Responses to nervous system stimulation are quick but short-lived; responses to endocrine system stimulation are typically slow but long-lasting
Define ‘homeostasis’
The maintenance of a constant internal environment
Explain the concept of homeostatic control
There is a range of normal values for blood glucose concentration, known as the set point. When the blood glucose concentration falls below or rises above the set point, cells in the pancreas detect changes and secrete insulin or glucagon depending on the change. This is known as negative feedback
