The Nervous System Flashcards
Nerve Impulse:
Electrical signal that travels along neurons.
Neuron:
A specialised cells transmitting nerve impulses.
Nerve:
A bundle of several neurones.
Examples of Reflexes:
Knee Jerk Reflex and Pupiliary Reflex
Three Types of Neurons:
Motor Neuron, Relay Neuron and Sensory Neuron
Cell Body:
The part of the neuron that contains the nucleus.
Axon:
Extension which carries nerve impulses to other neurones or effector organs (muscle or gland)
Dendrite:
Extensions at which nerve impulses are received from other cells synapses and transmitted to the cell body.
Myelin Sheath:
Fatty sheath which insulates the axon, which prevents short circuits of electrical impulses and speeds up the conduction of nerve impulses.
What is the Myelin Sheath made up of?
Schwann Cells
Reflex Arc
A very quick response from the sensory neurone to the motor neurone to the relay neurone.
The Spinal Cord is Enclosed By What?
Vertebral Column
What is the Spinal Cord?
A long thin tubular bundle of nerves.
Spinal Cord is an Extension From What?
The CNS from the Brain
Synapses:
The tiny gap between two neurones across which impulses pass by diffusion of a neurotransmitter.
Diffusion:
When there is high concentration in one place, whilst there is low concentration in the other. It when it spread to these areas of low concentration, we call in diffusion.
How do Synapses Function? Step 1?
The nerve impulse travels along the axon to the synapse in the form of an electrical signal.
How do Synapses Function? Step 2?
The vesicles containing the neurotransmitter move to the membrane.
How do Synapses Function? Step 3?
The neurotransmitter is moving into the space between the neurones (synapse)
How do Synapses Function? Step 4?
The neurotransmitter diffuses across the synapse (from high to low concentration)
How do Synapses Function? Step 5?
The neurotransmitter binds to the receptors on the surface of the dendrites
How do Synapses Function? Step 6?
Binding of the neurotransmitter triggers a new nerve impulse.
How do Synapses Function? Step 7?
The nerve impulse travels from the dendrite to the axon.
Neruotransmitters:
They transmit signals from one neurone to another across a synapse.
Neurotransmitters can either be…
Excitatory or Inhibitory
Three Examples of Neurotransmitters:
GABA, Seratonin, Dopamine
Seratonin affects…
Mood
Dopamine effects…
Movement
GABA produces a ….
Calming effect
Conjunctiva:
Layer covering the cornea and the sclera. Helps to lubricate the eye.
Cornea:
Clear covering of eye. Helps to refract and focus light.
Pupil:
Hold in the centre of the iris. Controls the amount of light entering the eye.
Iris:
Pigmented tissue, sphincter. Controls the amount of light entering the eye.
Suspensory Ligament:
Ligaments connecting the ciliary muscle and the lens. Involved in controlling accommodation (focusing).
Ciliary Muscle:
Ring of muscle connected to lens via suspensory ligaments. Controls accommodation (focusing).
Retina:
Inner layer of eye containing rods and cones. Responds to light stimulus.
Optic Nerve:
Sensory nerve (part of CNS). Carries nerve impulses from retina to brain.
Pupil:
Hold in the centre of the iris. Controls the amount of light entering the eye.
What is the RECEPTOR in the The Pupil Reflex?
Retina
What is the SENSORY NERVE in the The Pupil Reflex?
Optic Nerve
What is the EFFECTOR in the The Pupil Reflex?
Muscles in the Iris
Describe the Mechanism of the Pupil Reflex?
In the dark a reflex action occurs: the pupil gets large so that more light. An enter the eye and you can see the opposite happens in bright light. The pupil gets smaller and this stops too much light from entering the eye and damaging it. This all changes in the iris.
What happens to muscles in the iris in bright light?
The circular muscles contract and the radial muscles relax.
What happens to the muscles in the eye in dim light?
The radial muscles contract and the circular muscles relax.
Rods respond to…
Light
Cones respond to…
Colour
Photoreceptors:
Our retinas are covered with light sensitive cells called rods and cones. The rods detect the intensity of the light and allows us to see if thing are dark or light. The cones however detect the light. When there is little light, cones do not work as there is little light. There are three types of cones in the retina. Each is sensitive to a different colour: red, blue and green.
Accommodation:
The reflex that makes the eye focus on an object changing the shape of the lens.
How do we see?
Light reflected for an object is refracted by the cornea and the lens form an image of this object upside down on the retina. The brain interprets this image the right way up.
How is the eye able to focus of objects at different distances?
The lens shape is adjustable
How the eye focuses on a distant object?
The rays refract less and the lens are flatter.
Focusing on object that are nearby?
The lens are more circular and they are refracted more
How do we see?
Light reflected for an object is refracted by the cornea and the lens form an image of this object upside down on the retina. The brain interprets this image the right way up.
