Nervous System Flashcards
What is the nervous system divided into?
Central nervous system (CNS)
Peripheral nervous system (PNS)
What does the CNS consist of?
Encephalon and spinal cord
Covered by meninges (membranes)
Suspended in serebrospinal fluid (CSF)
What does the PNS consist of?
Cranial and spinal nerves
Ganglia
What does the brain stem consist of?
Nuclei of all but first 2 cranial nerves
Medulla, pons and midbrain
What does the cerebrum consist of?
Telencephalon - cerebral hemispheres
Diencephalon
What’s the telencephalon responsible for?
Motor and sensory
What’s the diencephalon responsible for?
Basic brain
E.g. ‘fight or flight’ , mating
What structures are included in the CNS?
Spinal cord
Brain stem
Cerebellum
Cerebrum
What are neurons?
Excitable nerve cells
Transmit information as electrical signals / action potentials
What does a typical neuron have?
Cell body (soma)
Neurite(s)
What’s a neurite?
A dendrite or axon
Structure of an axon:
Usually covered with myelin or Schwann cells
Structure of dendrites:
Multiple, thin, short extensions
What are neurons supported by?
Neuroglia (specialised glial cells)
Can regenerate
Glial cells (neuroglia) in PNS:
Satellite and Schwann cells
What do satellite cells do?
Support + monitor neurons
What do Schwann cells do?
Wrap around 1 axon
Filled with myelin - electrical insulation
What glial cells (neuroglia) are in CNS?
Oligodendrocytes
Astrocytes
Microglia
Ependymal cells
What do oligodendrocytes do?
Surround multiple axons with myelin sheaths
What do astrocytes do?
Involved with blood-brain barrier
What do microglial cells do?
Clear up dead neurons + cells
What do ependymal cells do?
Line inside of brain
Produce cerebralspinal fluid
What is myelin produced by?
Schwann cells in PNS
Oligodendroglia in CNS
Hat is myelin made up of?
Insulation material
Rich in lipid and protein
Importance of myelin sheaths around axons:
Faster conduction - less energy
How do neurons communicate?
Via synapses
Between axons and dendrites
What’s ganglion?
In PNS
Collection of nerve cell bodies outside CNS
What does grey matter predominantly consist of?
Cell bodies or neurons + neuroglia + unmyelinated neurites
Where is grey matter found?
Surface of cerebral + cerebellum hemispheres
Depths of cerebrum
Middle of spinal cord
What does white matter consist of?
Axons (usually myelinated)
Where is white matter found?
Deep in brain
Surface of spinal cord - surrounding grey matter
Direction of axons:
Up/down
Front/back
Left/right
What can be used to show many axons connecting specific areas of CNS?
Diffusion tensor imaging (MRI)
Generates 3D model
What’s the PNS divided into?
Sensory (afferent)
Motor (efferent)
What’s the difference between sensory and motor PNS?
Sensory is afferent (signals come in)
Motor is efferent (signals go out)
What can the sensory PNS be divided into?
Somatic sensory - conscious e.g. body wall + limbs
Visceral sensory - unconscious e.g. blood pH
What is motor PNS divided into?
Somatic motor - conscious
Visceral motor - unconscious e.g. smooth muscle
What is visceral motor in motor PNS further divided into?
Enteric - almost autonomous nervous system of gut
Parasympathetic
Sympathetic
What do afferent neurons do in sensory division?
Convey information from receptors in peripheral tissue and organs to CNS
What do efferent neurons do in motor division?
Transmit signals from CNS to the effector cell
What does sensory input do in the NS?
Monitors both external and internal environments
What can efferent division of the nervous system also be divided into?
Somatic and autonomic
What is involved with somatic NS?
Skeletal muscles
Voluntary
What is involved with autonomic NS?
Cardiac and smooth muscles
Glands
Important for internal homeostasis
Involuntary
What is the autonomic nervous system divided into?
Sympathetic and parasympathetic
Where is the sympathetic system found?
Thoracolumbar
Where is the parasympathetic system found?
Craniosacral
What’s sympathetic nervous system involved with?
Fight or flight e.g. increase heart rate
Activates body under conditions of emergency
What’s the parasympathetic system involved with?
Rest + digest e.g. decrease heart rate
Conserves body energy + maintains body activity at basal levels - homeostasis
Where are cell bodies in sympathetic system found?
At lateral horn of T1-L2 spinal cord segments
Where are cell bodies of parasympathetic system found?
At brain stem or S2-4 spinal cord segments
What are encephalon and spinal cored protected by?
Bones (skull bones + vertebrae)
Meninges
Cerebrospinal-spinal fluid
What are the three layers in the meninges?
Dura mater
Arachnoid mater
Pia mater
Structure of dura in meninges:
All around brain + spinal cord
Most superficial and toughest
2 layers - inner miningeal + outer periosteal
Why is there inward septae of dura?
Dura partitions
Secure brain to skull
Dampen movement of brain in cranial cavity
Divide cranial cavity into communicating compartments
Give examples of dura septae:
Falx cerebelli
Falx cerebri
What is the structure of arachnoid layer in meninges?
Close to dura
Web-like
What is the structure of pia in meninges?
Deepest layer
Direct contact with CNS tissue
Highly vascular
Enters every sulci
What spaces are found in meninges?
Epidural
Subdural
Subarachnoid
Epidural space:
Between dura and bone
Can bleed into it
Subdural space:
Potential space between dura and arachnoid
Can bleed into it
Subarachnoid space:
Between arachnoid + pia
Contains Cerebrospinal fluid + cerebral arteries
What are cerebral ventricles?
Interconnected spaces filled with cerebrospinal fluid
What are the cerebral ventricles?
Lateral ventricle
3rd ventricle
4th ventricle
Central canal
Where is the lateral cerebral vertical positioned?
Cerebral hemisphere
Where is 3rd cerebral ventricle positioned?
Diencephalon
Where is 4th cerebral ventricle positioned?
Brain stem
Where is the central canal positioned?
Spinal canal
What is cerebrospinal fluid?
Clear, cell free
Fills cerebral ventricles
Passes from cerebral ventricles to subarachnoid space
What is Cerebrospinal fluid produced by?
Choroid plexus in lateral and 3rd ventricles
Where does cerebrospinal fluid circulate?
Cisterns and subarachnoid space
What is cerebrospinal fluid absorbed by?
Arachnoid granulation into dural venous sinuses
What does the external surface of the brain look like?
Gyri - in folding of cerebral hemispheres (convolutions)
Gyri separated from each other by Sulci
Structure of cerebrum:
Two hemispheres divided by Median longitudinal fissure
What does each hemisphere in cerebrum consist of?
Cerebral cortex
Cerebral white matter
Nuclei
What are cerebral lobes?
Parts of hemispheres (telencephalon)
Formed by gyri and separated by sulci
What are the different cerebral lobes?
Frontal
Parietal
Occipital
Temporal
Limbic - binding lobe
Insula- deep
What can we use to determine the functions of different regions of the nervous system?
Lesion and outcome
Animal experiments
Functional imaging techniques (PET, fMRI)
Function of frontal lobe:
Motor
Function of parietal lobe:
Sensory
Function of occipital lobe:
Vision
Function of temporal lobe:
Auditory
Function of left hemisphere:
Language and maths
Function of right hemisphere:
Visual-spatial skills and creativity
Broca’s area:
Forming words
Wernicke’s area:
Understanding words
What’s involved with diencephalon?
Thalamus
Hypothalamus
Function of Thalamus:
Relay station for sensory impulses ascending to sensory cortex
Encloses 3rd ventricle
Function of hypothalamus:
Autonomic + endocrine control
Function of midbrain:
Superior and inferior colliculi (visual + auditory reflex centres)
Red nucleus (subcortical motor centre)
Substantial nigra (reward-seeking, motor learning)
What does the midbrain surround?
Cerebral aqueduct
Functions of Pons:
Conduction area between forebrain + cerebellum
Nuclei contribute to regulation of respiration, hearing + balance
Functions of medulla:
Pyramidal decussation before entering spinal cord
Vital centres - respiratory rhythm, heart rate
Non-vital centres - cough, sneeze
What is pyramidal decussation?
Crossing of corticospinal axons
Where are the 2 hemispheres in cerebellum?
Cerebellar fossa
Functions of cerebellum:
Processes + interprets impulses from motor cortex and sensory pathways
Coordinates motor activity for smooth movements - important for balance
What essentially is the spinal cord?
Two way impulse conduction pathway + reflex centre
What is the spinal cord protected by?
Vertebrae
Meninges
Cerebrospinal fluid
Where does the spinal cord extend from?
Extends from skull base (foramen magnum) to level of L1/L2 intevertebral disc or mid L2 vertebra
Doesn’t extend length of vertebral column
What are cervical and lumbosacral enlargements involved with?
Innervation of limbs
Where is the conus medullaris?
End of spinal cord
What does grey matter of spinal cord contain?
Dorsal/posterior horns
Lateral horns
Ventral/anterior horns
What does white matter of spinal cord consist of?
Ventral/anterior columns
Lateral columns
Dorsal/posterior columns
What can the spinal cord be divided into?
Segments - associated with one pair of spinal nerves
What segments is the spinal cord divided into?
Cervical (8)
Thoracic (12)
Lumbar (5)
Sacral (5)
Coccygeal (1)
What is Cauda equina?
Roots of lumbar and spinal nerves
