Compendium 8 / 9. The Nervous System Flashcards
What are the 2 structural divisions of the nervous system?
- The CNS
2. The PNS
What are the 3 functional divisions of the nervous system?
- Autonomic
- Somatic
- Enteric
What are the roles of afferent nerves?
Also known as sensory
To take information TO the CNS.
What are the roles of efferent nerves?
Also known as motor
To take information AWAY from the CNS
Explain the pathway of an afferent neuron
- A sensory receptor picks up a stimulus
- The afferent neuron ends in the CNS (spinal cord)
- The cell bodies reside in the dorsal root ganglion
Explain the pathways of efferent neurons
Autonomic :
- The first motor neuron takes the nerve impulse from the CNS (via the ventral root) to the autonomic ganglion.
- The impulse transfers to the second motor neuron in the autonomic ganglion.
- The impulse is then taken to the effector organ by the second motor neuron.
Motor :
1. The nerve impulse is taken straight from the CNS to the effector organ via the ventral root.
Define plexus
An extensive network of cell bodies or axons.
What are synaptic knobs?
The small baubles on the end of the synaptic terminals.
What are the 3 structural classifications of neurons?
- Multipolar
- A single axon
- Many dendrites - Bipolar
- A single axon
- A single dendrite from the cell body
- Extremely rare - Unipolar
- The cell body is positioned to the side of the axon
What are the 4 types of neuroglia cells?
- Astrocytes : Allow for communication for blood vessels and neurons and create a barrier around injured cells
- Ependymal cells : Cilia allow for the movement of CSF
- Microglia : Monitor and protect surrounding neurons
- Oligodendrocytes : Form the myelin sheath around axons
What are the 2 types of cells found in the PNS?
- Schwann cells/neurolemmocytes : Make up the myelin sheath around axons
- Satellite cells : Provide support and nutrition
What is a membrane potential?
The difference of charge across the cell membrane
What are non-gated ion channels also referred to as?
leak channels
Are there more non-gated channels for potassium or sodium?
potassium
What are the 3 types of gated ion channels?
- Ligand-gated ion channels - opens when a ligand such as a hormone binds to them.
- Voltage-gated ion channels - opens when an electrical current passes through the membrane
- Other-gated ion channels - opens when there is change of temperature or pressure
What is resting membrane potential?
When the in intracellular fluid of a cell is more negative compared to the extracellular fluid
What is depolarisation?
When the membrane potential suddenly becomes more positive
What is hyperpolarisation?
When the membrane potential becomes more negative
What is repolarisation?
When the membrane potential returns to normal.
What are graded potentials?
- Short lived, localised changes in a membrane potential
- They can lead to action potentials
What is the all-or-nothing principle?
The graded potential must be strong enough to surpass the threshold
What is the refractory period?
When a particular part of the cell membrane is engaged with an impulse and cannot take on another impulse.
What are the 2 different types of synapses?
- The electrical synapse - the current jumps between synapses
- The chemical synapses - chemicals act as carriers
How are neurotransmitters removed?
- They are broken down by enzymes
- Re-absorbed back into presynaptic terminal
What are reflexes?
Automatic responses to a stimulus
What are the 5 components that make up a reflex?
- A sensory receptor
- A sensory neuron
- A interneuron
- A motor neuron
- A effector organ
What are the 5 regions of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Sacral
- Coccygeal
How many pairs of spinal nerves are there?
31
How many vertebral bones are there?
30
What are the meninges?
The connective tissue covering the spinal cord and brain
What are the 3 layers of meninges?
- dura mater
- arachnoid mater
- pia mater
What are the 3 layers of connective tissue that surrounds cells of the PNS?
- endoneurium - surrounds each axon and it’s Schwann cell
- perineurium - surrounds nerve fascicles
- epineurium - surrounds a group of fascicles
What are nerve fascicles?
A group of axons
What are the 3 structural divisions of the brain?
- The forebrain
- Cerebrum
- Diencephalon - Midbrain
- Hindbrain
- Pons
- Medulla Oblongata
- Cerebellum
What are the four parts of the diencephalon of the forebrain?
- Thalamus
- Subthalamus
- Epithalamus
- Hypothalamus
What are gyri?
Elevated tissue or folds on the cerebrum
What are sulci?
Grooves within the cerebrum
What are fissures?
Deep grooves within the cerebrum
What is the lateral fissure?
Separates the left and right hemispheres of the brain
What is the central fissure?
Separates the frontal lobe from the parietal lobe
What are the 5 lobes of the cerebrum?
- Frontal
- Parietal
- Temporal
- Occipital
- Insula
What is the role of the thalamus?
- It acts as a gateway to the cerebrum for sensory information.
- Regulates mood, memory and strong emotions
What is the role of the hypothalamus?
- Maintains homeostasis via the endocrine system
- Regulates many of the body’s necessary functions
(body temp, digestive activities, sex drive etc).
What is the role of the frontal lobe?
- Voluntary motor function
- Higher functional thinking
What is the role of the temporal lobe?
- Receives and processes smell and hearing
- Has a role in memory
What is the role of the parietal lobe?
- Receives majority of touch/physical sensory input
What is the role of the occipital lobe?
- Receives vision input
What is the role of the insula lobe?
- Receives and processes taste information
What is the role of the midbrain?
- Receives visual, auditory and tactile sensory information
- Generates reflexes of the head, eyes and body
What is the role of the medulla oblongata?
- The home for the cardiovascular centre and respiratory centre
- Controls reflexes such as swallowing, vomiting, hiccupping etc.
What is the role of the pons?
- Communicates to different parts of the brain
- Contains the sleep centre
What is the role of the cerebellum?
- Controls smooth movement / locomotion etc balance and coordination
What parts of the brain make up the brainstem?
- Midbrain
- Pons
- Medulla Oblongata
Describe autocrine communication
- Chemicals that have an effect on the same cell type as the one they were released from
- Local
Describe paracrine communication
- Chemicals released by cells that affect other cells without being transported in the blood
Describe neurotransmitter communication
- Chemicals produced by neurons and secreted into extracellular spaces by presynaptic nerve terminals
- Travel short distances
- Influence post synaptic cells
Describe endocrine communication
- Chemicals produced by cells and enter the circulatory system to affect distant cells
What are the hormones released by the anterior lobe of the pituitary gland?
- FSH
- LH
- GH
- TSH
- ACTH
- Prolactin
What are the hormones released by the posterior lobe of the pituitary gland?
- Oxytocin
- Antidiuretic hormone
