Nervous System Flashcards
What are the three types of Neurons and their function?
Sensory Neurons (detect), Interneurons (process) and Motor Neurons (respond)
What do Neurons do?
They receive input, conduct action potentials and release neurotransmitters throughout the body.
What do glial cells do?
Support neuron function, form myelin sheath on axons, form blood-brain barrier and provide nutrients, support and waste removal in ECF of brain.
What is the Myelin Sheath?
Causes action potentials to conduct faster down the axon, reduce sodium leaking out
Brain neurons create a complex network with axons that send signals:
From the front to the back of the brain, to neighbouring neurons and from left to right hemisphere and vice versa.
What is the Central Nervous System made of?
The brain and spinal cord (made of neurons and glial cells closely packed together)
What is the Peripheral Nervous System made of?
Peripheral Nerves (made of sensory and motor axons packed together)
What is Sensory Information?
Information is sent from the sensors into peripheral nerves to the spinal cord and brain
What is Motor Information?
Information sent to the spinal cord and brain into peripheral nerves to control muscle
What is transduction?
To convert or change from one form to another
What is sensory transduction?
The conversion of a sensory stimulus into action potentials
How are sensory receptors categorised?
By the type of stimuli they can detect and transduce. (eg. thermoreceptors (temperature), osmoreceptors (osmolarity), chemoreceptors (chemicals), photoreceptors (light), nocioreceptors (pain), mechanoreceptors (pressure, stretch, motion)
What are Somatic Receptors?
They detect stimuli from the external environment
In skin, skeletal muscle and special sensors (eg. nose)
What are Visceral Receptors?
They detect stimuli from the internal environment
In internal organs (viscera), glands and blood vessels
Somatic Sense: Vision
Transduction of light into electricity (action potentials)
Light enters photoreceptors at the back of the eye
Light causes ion shifts inside photoreceptor cells
Creating action potentials, sent to the brain along axons
Brian interpretation = visual images
Somatic Sense: Vestibular
Transduction of motion into electricity
Movement of the head causes deformation of inner ear cells
This allows ions to enter and depolarise the cells
Creating action potentials, sent to the brain along axons
Brain interpretation = head movement and orientation
Somatic Sense: Proprioception (limb muscle)
Transduction of stretch into electricity
Stretch of the sensory neuron endings in muscle, tendon or skin
Physically pulls on the membrane allowing ions to enter neurons
Creating action potentials, sent to the brain along axons
Brain Interpretation = location of each limb in relation to the torso
Visceral Sense: Pressure
Transduction of pressure: Baroreceptors transduce pressure changes into action potentials
Pressure deforms membrane, allowing ions to move, leads to depolarisation
Action potentials are sent to the brain and/or result in stimulation and contraction/dilation of smooth muscle
Visceral Sense: Blood Osmolarity
Transduction of osmolarity: Osmoreceptors in the hypothalamus transduce osmolarity changes into action potentials
Osmolarity affects certain channels, affecting ion movement and depolarisation
Action potentials are sent to stimulate release of hormones to correct osmolarity changes
Visceral Sense: Blood Acidity (pH)
Transduction of acidity: chemoreceptors transduce changes in blood CO2 and H+ levels in action potentials
CO2 and H+ levels affect various receptors in complex interactions, leading to depolarisation
Action potentials are sent to respiratory control neurons in the brain stem that monitor and control blood acidity
What is a sensory unit?
Nerve endings and the sensory neuron they attach to
What is a receptive field?
The area of detection where nerve endings are.
Areas of the skin with large, widely spread receptive fields detect less detail (eg. arms and legs).
Areas of the skin with small, closely packed receptive fields can detect more detail (eg. fingertips and lips)
Receptive Fields and the Somatotopic Map
Body parts with more sensory neurons = more representation in the brain.
1 sensory neuron per receptive field.
Simulus Intensity
Mild stimuli cause few action potentials
Intense stimuli cause many action potentials