Nervous System Flashcards
What forms the PNS?
+ Cranial and spinal nerves
+ Ganglia
What forms the CNS?
+ Brain
+ Spinal cord
What are the basic building blocks of the nervous system?
+ Neurons
+ Glia
What are the structural components that make up neurons?
+ Axon
+ Dendrites
+ Cell body
What are the different types of glia cells?
+ Astrocyte
+ Oligodendrocyte
+ Microglia
How do neurons communicate?
Via synapses between axons and dendrites
What does grey matter comprise of?
Cell bodies of neurons
What does white matter comprise of?
Axons
What are the functional division of the nervous system?
+ Sensory (afferent)
+ Motor (efferent)
What is the function of the sensory division of the nervous system?
+ Carries information towards the CNS
+ Responsible for acquiring and processing information from the environment
What is the function of the motor division of the nervous system?
+ Information is going from the CNS to effector organs
+ Responsible for generating movements and other behaviours
What are the two different efferent divisions?
+ Somatic (voluntary)
+ Autonomic/visceral (involuntary)
What are features of the somatic division?
+ Motor axons connecting CNS to skeletal muscles
What are features of the autonomic/visceral division?
+ Motor axons that innervate cardiac and smooth muscle, glands
+ Important for internal homeostatis
What are the divisions of the autonomic nervous system
+ Sympathetic (thoracolumbar, fight or flight)
+ Parasympathetic (craniosacral, rest and digest)
What are the features of the sympathetic nervous system?
+ Activates the body under conditions of emergency
\+ Dilates pupils \+ Increases heart and respiratory rates \+ Increases blood pressure \+ Increases blood glucose levels \+ Dilation of bronchioles \+ Induces sweating
+ (During exercise) sympathetic vasoconstriction shunts blood from the skin and digestive viscera to the heart, brain and skeletal muscles
+ Preganglionic sympathetic neurons arise from later horns of T1-L2
What are features of the parasympathetic nervous system?
+ Conserves body energy and maintains body activities at basal level (homeostasis)
+ Pupillary constriction
+ Glandular secretion
+ Increase in digestive tract mobility and smooth muscle activity, leading to elimination of faeces and urine
+ Parasympathetic preganglionic neurons arise from brain stem and from S2-S4
What forms the two neuron chains of the autonomic nervous system?
Cell body of pre-ganglionic neuron in CNS synapses with the cell body of the post-ganglionic neuron in a ganglion
Where are sympathetic ganglia located? Describe their synaptic fibres
+ Located close to the spinal column therefore:
- pre-synaptic fibres are short - post-synaptic fibres are quite long
Where are parasympathetic ganglia located? Describe their synaptic fibres
+ Located close to the organ they innervate therefore:
- pre-synaptic fibres are quite long
- post-synaptic fibres are short
What features protect the CNS?
+ Skull and vertebral column
+ Meninges
+ CSF
Where are the meninges relative to the brain, spinal cord and their blood vessels?
It encloses them
What are the 3 protective tissue layers that form the meninges?
+ Dura
+ Arachnoid
+ Pia
What are features of the dura?
+ Most superficial
+ Strongest/toughest
+ Usually in contact with bone
What are features of the arachnoid?
+ Adhered closely to the dura
+ Web-like in appearance
What are features of the pia?
+ Deepest layer
+ In direct contact with CNS tissue
What is the function of the subarachnoid space?
It contains CSF
What is the function of the folds of dura matter?
Inward folds of dura (dural partitions) secure the brain to the skull, dampening movement of the brain in the cranial cavity
Besides the subarachnoid space, where else does CSF occupy?
Spaces within the CNS
What is the function of ventricles in the brain?
They are the site of CSF production due to each ventricle being a region of choroid plexus, a network of ependymal cells involved in the production of CSF
How many ventricles in the brain are there and where are they located?
+ Lateral ventricle: cerebral hemisphere
+ 3rd ventricle: Diencephalon
+ 4th ventricle: Brain stem
+ Central Canal: spinal cord
What is CSF?
+ Cerebrospinal fluid
+ Clear, cell-free fluid
+ Produced in the choroid plexus that circulates in the subarachnoid space
What are the main divisions of the brain?
+ Cerebrum
+ Diencephalon
+ Brain stem
+ Cerebellum
What are the lobes of the cerebrum?
+ Frontal lobe
+ Parietal lobe
+ Occipital lobe
+ Temporal lobe
What are sulci?
Inward folds of the cerebral hemispheres that form ‘valleys’ between the gyri
What are gyri?
Ridges of the inward folded cerebral cortex
What structures does the cerebrum consist of?
\+ (Median) Longitudinal Fissure \+ Cerebral Cortex (grey matter) \+ Cerebral white matter \+ Corpus Callosum \+ Ventricles \+ Caudate \+ Internal Capsule \+ Putamen
What are the different functional areas of the cerebrum?
+ MOTOR: primary motor and premotor in FRONTAL lobe
+ SENSORY: primary somatosensory and somatosensory association areas in PARIETAL lobe
+ VISION: primary visual and visual association areas in OCCIPITAL lobe
+ AUDITORY: primary auditory and auditory association areas in TEMPORAL lobe
What is the role of the hemispheres?
Each hemisphere receives sensory impulses from, and dispatches motor impulses to, the opposite side of the body
Hemispheres show lateralisation of cortical function, what is the function of each hemisphere?
+ Left hemisphere: dominant, specialised for language and maths skills
+ Right hemisphere: specialised for visual-spatial skills and creativity
What is Broca’s area?
+ Region of the frontal lobe
+ Located within the left hemisphere
+ Motor speech: linked with speech production
What is Wernicke’s area?
+ Region of temporal lobe
+ Located within left hemisphere in cortex
+ Sensory speech: linked to understanding speech
What is the role of the thalamus?
It is a major relay station for:
- sensory impulses ascending to sensory cortex
- inputs from subcortical motor nuclei and cerebellum travelling to cerebral motor cortex
What is the role of the hypothalamus?
+ Important autonomic control centre
\+ Maintains water balance \+ Regulates thirst and eating behaviour \+ Regulates GI activity \+ Regulates body temp. \+ Regulates activity of anterior pituitary gland
+ Encloses 3rd ventricle
What areas form the brainstem?
+ Midbrain
+ Pons
+ Medulla Oblongata
What does the midbrain contain?
+ Superior and inferior colliculi (visual and auditory reflex centres)
+ Red nucleus (subcortical motor centre)
+ Substantia nigra (involved in rewards seeking, motor learning etc.)
Where does the midbrain surround?
The cerebral aqueduct
What are the functional features of the pons?
+ Conduction area (connections between forebrain and cerebellum)
+ Nuclei contribute to regulation of respiration as well as hearing and balance
What are the functional features of the medulla oblongata?
+ Pyramidal decussation (crossing of corticospinal axons) before entering SC
+ Vital centres regulating: respiratory rhythm, heart rate, BP
+ Non-vita centres regulating: coughing, sneezing, swallowing, vomiting
What are features of the cerebellum?
+ 2 hemispheres marked by convolutions with an internal grey matter nuclei surrounded by white matter and an outer cortex of grey matter
+ Connects to brain stem by cerebellar peduncles (superior, middle, inferior)
+ Processes and interprets impulses from motor cortex and sensory pathways and coordinates motor activity for smooth, well-timed movements
+ Important for balance
What are features of the spinal cord?
+ Two-way impulse conduction pathway and reflex centre
+ Resides within the vertebral column
+ Protected by the meninges and CSF
+ Extends from foramen magnum to end of L1 vertebra (does not extend full length of vertebral column)
Describe the grey matter in a transverse/cross section of the spinal cord
H-shaped, contains neuronal cell bodies within ‘horns’:
+ Lateral: visceral/autonomic motor neurons
+ Ventral/anterior: somatic motor neurons
+ Dorsal/posterior: interneurons
Describe the white matter in a transverse/cross section of the spinal cord
Columns containing a number of ascending and descending tracts - all paired and most decussate.
+ Ventral/anterior columns
+ Lateral columns
+ Dorsal columns
What are other landmarks of the transverse/cross section of the spinal cord?
+ Posterior median fissure
+ Anterior median fissure
+ Anterior white commissure
+ Central canal
How many pairs of spinal nerves are there?
31 pairs
How many paired spinal nerves are there in each of the 5 regions?
Cervical (8) Thoracic (12) Lumbar (5) Sacral (5) Coccygeal (1)
What is the name for where the spinal cord terminates?
Conus Medullaris (end of L1)
What are the roots of the spinal cord called?
Cauda Equina (L, S, C)
Why are some areas of the spinal cord enlarged?
They are areas of control (spinal nerves innervating the limbs)
What are the areas of the spinal cord that are enlarged?
+ Cervical
+ Lumbosacral
What are the features of a dorsal (spinal) root ganglion?
+ Dorsal rami
+ Ventral rami
+ Rami communicates
+ Sympathetic ganglion
