The Nervous System Flashcards
What is the nervous system?
-The nervous system is a complex network of nerves and cells
that carry messages to and from the brain and spinal cord to
various parts of the body
-The nervous system includes both the central nervous
system and peripheral nervous system
What is the central nervous system?
Brain and spinal cord
· Integrates, processes and coordinates sensory data and motor commands
What is the peripheral nervous system?
(nerves that aren’t in our brain and spinal cord)
· Neural tissue outside CNS
· Delivers information to CNS
· Somatic nervous system – voluntary & involuntary (automatic)
· Autonomic nervous system
→ Sympathetic
→ Parasympathetic
Cells types are neurons and neuroglia
Are motor neurons afferent or efferent?
They are efferent
Are sensory neurons afferent or efferent?
They are afferent
What are dendrites?
Dendrites extend out from cell body, highly branched, neurons receive info from other neurons at the dendrites, large surface area
What are schwann cells
Form the myelin sheath insulating and protecting the axon
What are axons?
long cytoplasmic process, propagates an action potential
What are Telodendria?
terminal branches or synaptic terminals
What is the myelin sheath?
The insulating envelope of myelin that surrounds an axon and facilitates the transmission of nerve impulses
What are nodes of Ranvier?
A gap in the myelin sheath of a nerve, between adjacent Schwann cells
What is an action potential?
Action potential is a short-lasting event in which the membrane potential of a neuron rapidly rises and falls
How is an action potential generated?
- Voltage gated sodium and potassium channels on the membrane (resting potential of -70mV)
- Threshold is -55mV
- Na channels open and flow by the electrochemical gradient because it is positively charged the membrane potential increases to +30 mV
- Na channels close and K channels open
- K leaves the cell
- Repolarisation -70mV, K channels close
Role of the Na and K pump?
-In an AP, depolarisation results from an influx of Na ions
-Repolarisation results from the loss of K ions
The Na/K exchange pump returns intracellular & extracellular ion levels back to resting levels
-Pump requires ATP
What is continuous conduction?
-Non-myelinated neurons- just the axon
-Slow process
-AP moves by continuous propagation down the axon
-Depolarisation spreads from one adjacent region to the next
What is saltatory conduction?
Myelin limits movement of ions across the membrane
AP ‘jumps’ from one node of Ranvier to the next
Fast process
What is the effect of the axon diameter?
A thicker axon means more cytoplasm
Axon diameter, as well as presence of myelin, speeds up the process.
This is because, cytoplasm shows less resistance to ion movement than plasma membrane
Therefore in larger axons the depolarisation moves along more quickly
What is a synapse?
A gap between two neurons.
What events take place at the synapse?
- Acetylcholine (ACh) is the most common neurotransmitter
- Excitatory neurotransmitter
- Causes depolarisation and propagation of AP
- Inhibitory neurotransmitter
- Causes hyperpolarisation and suppression of AP
- Cholinergic synapse (where we get ACh)
- Acetylcholinesterase breaks it down to aloow the receptor to be inactivated and used again
What is a monosynaptic reflex?
-Stretch reflex
-No interneuron, sensory neurons act directly on motor neuron in spinal cord
-Fast response
-Patellar reflex
What is a polysynaptic reflex?
Produce more complex responses
Interneurons can control motor neurons in several muscle groups simultaneously
Brain- What is the function of the meninges?
tough, fibrous, this and CSF provide a cushion for the brain inside the skull
Brain-What is the medulla?
involuntary functions, contains the cardiac, respiratory, vomiting and vasomotor centres and therefore deals with the autonomic (involuntary) functions of breathing, heart rate and blood pressure. Cannot live without it
Brain- What is the Pons?
Relays messages from forebrain to cerebellum, involved in sleep, respiration, hearing, taste, eye movement etc
Brain- What is the cerebrum?
largest part of the human brain, associated with higher brain function such as thought and action.
Brain- What is the cerebellum?
coordinated muscular activity at subconscious level
Brain- What is the function of the midbrain?
regulates auditory and visual reflexes
Brain- What is the thalamus?
relay motor and sensory signals to the cerebral cortex
Brain- What is the hypothalamus?
control hormone production and body temp
What is the automatic nervous system?
Responsible for control of the bodily functions not consciously directed, such as breathing, heartbeat and digestive processes
What are sympathetic neurones?
-They produce a ‘Fight or flight’ response
-Constantly active at a basic level to maintain homeostasis
-Uses energy and increases metabolic rate
-Noradrenaline released at NMJ
-Dilate pupils, heart rate increases, skeletal muscle blood vessels dilate, GIT blood vessels constrict
What are parasympathetic neurons?
-‘Rest and digest’ response
-Conserves energy and lowers metabolic rate
-ACh released at NMJ
-Constriction of pupils, secretion by digestive glands, secretion of hormone, increase in smooth muscle activity of GIT, reduction in heart rate
-Complementary to sympathetic system
