9. Central Nervous System Flashcards
Receptors
SOMATIC: monitor outside world
VISCERAL: internal conditions
Where do receptors feed into?
Afferent division of the peripheral nervous system
Brings information to CNS
What occurs in the CNS?
Information processing and coordination of sensory input and motor commands
What are the 2 divisions of the efferent peripheral nervous system?
Somatic
Autonomic
What are the effector(s) of the somatic nervous system?
Skeletal muscle
What are the 2 divisions of the autonomic nervous system?
Sympathetic
Parasympathetic
What are the effector(s) of the autonomic nervous system?
Smooth muscle
Cardiac muscle
Glands
What does having a highly folded core allow humans to have?
More neurones
Thus be smarter animals
What is the role of the cerebellum?
Coordinates complex somatic motor patterns
What are the 2 parts of the diencephalon?
Thalamus: Integration centre for somatic and special sensory info and projection to cortex. Involved in emotional status, consciousness, appropriate motor response.
Hypothalamus: integration hub. Regulates temperature, emotion, hunger, thirst, hormone and autonomic function
What lies beneath the corpus callosum?
Diencephalon
What structure connects the right and left hemispheres?
Corpus Callosum
What is the role of the cerebrum?
Conscious thought processes, intellectual functions
Memory storage and processing
Conscious and subconscious regulation of skeletal muscle contraction
What is the role of the midbrain?
Processing visual and auditory data
Generation of reflexive somatic motor responses
Maintenance of consciousness
What is the role of the pons?
Relays sensory info to cerebellum and thalamus
Subconscious somatic and visceral motor centres
What is the role of the medulla oblongata?
Relays sensory info to thalamus and brain stem
Autonomic centres for regulation of visceral function
Difference between meaning of “ventral” in body and brain
Body: Towards abdomen
Brain: Inferior
Difference between meaning of “dorsal” in body and brain
Body: Towards back
Brain: Superior
What makes the pons recognisable?
It bulges anteriorly
Describe the spinal cord
33 vertebrae
31 pairs of nerves (in cervical segment there are 7 vertebrae and 8 nerves)
What are the hole in the vertebral column that spinal nerves pass through called?
Intervertebral Foramina
Spinal cord and vertebral column relative lengths
Spinal cord is shorter than the vertebral column: finishes at L1/L2
Below this is just emergence of nerves.
What is the consequence of there being no nervous tissue in lumbar cistern?
Provides safe site for lumbar puncture, usually between L3 and L4
List the groups of vertebral segments
Cervical Thoracic Lumbar Sacral Coccygeal
What does each spinal cord segment innervate?
A particular skin area (Dermatome)
A particular muscle area (Myotome)
Cauda equina
=Bundle of nerve fibres
Diameter varies throughout spinal cord
What is in the core of grey matter in the spine?
Cell bodies of neurones
What are in the bundles of white matter surrounding the grey matter core?
Myelinated axons
What does the Dorsal horn contain?
Cell bodies receiving sensory information
What does the Ventral horn contain?
Cell bodies of motor neurones
List 4 functions of the spinal cord
- Connects the peripheral nervous system to the brain
- Carries sensory signals to the brain
- Carries motor signals to the muscles
- Coordinates reflexes
What is the name of the area inside the vertebral canal beneath the point at which the spinal cord ends?
Lumbar Cistern
What is the name of the structure in the Lumbar cistern?
Cauda Equina
What is the difference between the dorsal horns and the ventral horns?
Dorsal horns are SENSORY: the impulses come towards the CNS
Ventral horns are MOTOR: the impulses go away from the CNS
How did the brain initially develop and what do the 3 parts of this initial brain differentiate into?
Initially developed as the forebrain, midbrain and hindbrain.
Forebrain became the cerebral hemisphere and diencephalon
Midbrain remained as the midbrain
Hindbrain became the pons, medulla and cerebellum
What is the brainstem composed of?
Midbrain
Pons
Medulla oblongata
What is the cerebrum composed of?
Cerebral hemisphere and diencephalon
Positioning of the brainstem
Continues down to the top of the spinal cord
What originates from the brain stem?
10 Cranial nerves
Control basic functions e.g. breathing, swallowing
What are the cerebral hemispheres comprised of?
Cortex
Basal ganglia
What are the 2 basal ganglia, what are they comprised of?
Corpus Striatum: Caudate + Putamen
Lentiform nucleus: Putamen + Globus Pallidus
What is the function of basal ganglia?
Control of movement:
Facilitating voluntary movement
Inhibiting unwanted or inappropriate movements
“Fine tuning”
Describe the cerebral cortex
2-4 mm thick ~30% exposed 70% within sulci (grooves) Deeply divided by fissures Highly folded into gyrus Laminar= 6 layers in most of cortex Somatotopic- “has a map of body”, each part of body is represented on cortex, size dependent on sensitivity
What is the limbic system involved in?
Motivation
Instinctive behaviour
Emotion
Memory
How is the cerebellum attached to the brainstem?
Attached to the brainstem posteriorly, by 3 pairs of peduncles
Structure of cerebellum
Grey cortex on surface (with deep parallel folds, folia)
Deeper white matter, with nuclei.
2 hemispheres divided in lobes, central vermis
What is the cerebellum connected to?
Vestibular system for balance
Spinal cord and muscles of locomotion, posture; muscle tone
Motor cortex and thalamus for learned movements (e.g. manual skills, trajectory, timing, speed and force)
What are Commissural fibres?
Connect 2 parts of the brain (1 from each side) e.g. Corpus callosum
What are association fibres?
Connect different structures on the same side
What are projection fibres?
are vertical
e.g. Sensory fibres from spinal cord fan out to project to a wide area of the cortex and corona radiata
Why does the nervous tissue of the brain need to be protected? How is it protected?
Nervous tissue is fragile
Protected by the cranium
What is the function of the meninges?
Protection
What are the 3 layers of the meninges?
Dura mater (outer): 2 layers
space between
Arachnoid mater (middle): holds vessels in place
Sub-arachnoid space: filled with CSF, vessels run through here
Pia mater (Inner)
Describe the ventricular system of the brain.
2 large lateral ventricles (C shaped), 1 for each cerebral hemisphere.
Lateral ventricles narrow and form the 3rd ventricle, which is in the diencephalon
3rd ventricle narrows to form the cerebral aqueduct, which passes down through the midbrain and becomes a tent-shaped structure called the 4th ventricle.
4th ventricle is behind the pons and medulla and in front of the cerebellum.
4th ventricle then narrows to form the central canal, which runs down the spinal cord.
Where is cerebrospinal fluid produced?
Choroid plexus (a special type of ependymal cell found in the ventricles)
Where does CSF leave the ventricles and enter the subarachnoid space?
CSF leaves the ventricles in the 4th ventricle, which has small holes in it
How is CSF reabsorbed into the venous system?
CSF is reabsorbed into the venous system by arachnoid villi
How much CSF is produced per day?
~500ml
Describe the composition of CSF
Similar to plasma (high Na+, low K+) but: Lower glucose Much lower protein Lower Ca2+, K+ Higher Cl-, Mg Slightly lower pH (7.33)
5 functions of CSF
Cushioning Nutrition Removing waste Immune cells Diagnostic
