Week 4: Structure of the Nervous System Flashcards
Components of the CNS
Brain
Spinal Chord
Components of the PNS
Nerves
Peripheral ganglia
Front (neuraxis)
Ventral
Back (neuraxis)
Dorsal
Top (neuraxis)
Rostral or anterior
Bottom (neuraxis)
Caudal or posterior
Outwards (neuraxis)
lateral
Inwards (neuraxis)
medial
Ipsilateral
structures Located on the same side of the
body/Neuraxis
Contralateral
structures Located on opposite side of the
body/neuraxis
Corpus callosum
Largest bundle of axons that connects left and right hemisphere
Evidence of Contralateral function
Split-brain patient Joe
Evidence of lateralization and localization
Non-fluent aphasia (Broca’s Aphasia) - damage to left frontal cortex (Inferior frontal gyrus, a.k.a. Broca’s Area)
Wernicke’s Aphasia – fluent aphasia; left, posterior
portion of superior temporal gyrus.
Forebrain (Telencephalon) consists of:
Cerebral cortex
Limbic system
Basal ganglia
Cerebral cortex consists of what parts:
frontal
parietal
temporal
occipital
Limbic system consists of:
olfactory bulb
amygdala
hippocampus
cingulate gyrus
Basal ganglia consists of:
Striatum
globus pallidus
Forebrain (diencephalon) consists of:
Thalamus
hypothalamus
Midbrain consists of:
Tectum
tegmentum
Hindbrain consists of:
pons
cerebellum
medulla oblongata
Cerebral cortex
- Most prominent part of the brain
- Convoluted by sulci/fissures and gyri
- Made up of neurons and glia (Gray Matter)
- 6 distinct layers/laminae
Frontal lobe
abstract reasoning, emotion, personality, decision making, executive function, motor movement (precentral gyrus)
Parietal lobe
numerical information, and integrates spatial information, processes sensory info (postcentral gyrus/primary sensory cortex)
Occipital lobe
vision perception (striate cortex/primary visual cortex damage and cortical blindness
Temporal lobe
auditory information, memory and learning, language, facial recognition, emotion and motivation
cortical homunculus
How our bodies are represented in the brain
Mapping functions of various brain regions
Limbic system
forms the epicentre of emotion and behavioural expression
implicated in: emotions(fear), anxiety, depression, Alzheimer’s disease
Basal ganglia
Bundles of subcortical nuclei that lie beneath the lateral ventricles, lateral to thalamus
◦ Important for motor movement
◦ Procedural learning
◦ Reward system
Basal Ganglia Implicated in:
* Parkinson’s
* Schizophrenia
* OCD
Forebrain
the Smaller portion of the forebrain that surrounds the third ventricle
thalamus
Projection fibers connect to the cortical surface to relay sensation, spatial and motor signal information
- Acts as a gateway to higher cortical function
- Regulates consciousness, sleep, alertness
hypothalamus
◦ Controls the autonomic nervous system and endocrine system
◦ Fighting, feeding, feeling, mating, sleeping, drinking (i.e., Motivational Behaviors)
◦ Releases it’s neurohormone via the pituitary gland
◦ The anterior pituitary is the Master Gland - releases tropic hormones that control secretion and production of hormones in other glands of the endocrine system
Tectum
◦ “Roof” of the midbrain
◦ Dorsal portion of the midbrain
◦ Swelling on each side are superior and inferior colliculus
Superior = visual processing and eye movements
Inferior = auditory processing
tegmentum
◦ “Floor” of the midbrain
◦ Includes periaqueductal gray matter (PGM), ventral tegmental area (VTA) and substantia nigra
◦ PGM: important for species-specific behavior (e.g., freezing, mating behavior)
◦ VTA: projections of DA neurons from VTA to nucleus accumbens (mesolimbic; motivation and reward) and from VTA to PFC (mesocortical; cognitive function)
◦ Substantia Nigra: DA projections from Substantia nigra to striatum (nigrostriatal; movement
Cerebellum
“Little brain”
◦ Vital for standing, walking, coordination, and sense of timing of external stimuli
◦ Integrates information from various senses
◦ Important for attentional control and some forms of memory
Pons
“bridge”
◦Relays info between the cerebral cortex and the cerebellum and spinal cord
◦Connected to cranial nerves that control sensations and movement of head (skin, eye movement, face, hearing)
Medulla Oblongata
◦Most caudal (posterior) part of the brain stem, sitting above the spinal cord
◦Important for cardiac, respiratory, vomiting, sneezing, salivation, coughing, and vasomotor function
◦Connected to cranial nerves that controls sensations and movement of head (taste, tongue, neck; vagus nerve)
Hemispherectomy due to Rasmussen’s disease demonstrates…
brain plasticity
Spinal chord
◦The cord of nervous tissue within the spinal column
◦Segmented structure –with sensory nerve (dorsal) and motor nerve (ventral) on left and right side
*Protected by the vertebral column
*Spinal nerves are formed at 31 places along spinal cord
*Spinal cord passes though the hole of the spinal foramen
*dorsal (afferent) and ventral (efferent) roots form spinal nerves
Bell-Magendie Law
afferent fibers are dorsal fibers and efferent fibers are ventral fibers
How many vertebrae in the spinal chord?
24
Cervical nerves - CNS
(nerves in the neck) supply movement and feeling to the arms, neck and upper trunk. Also controls breathing.
Thoracic nerves - CNS
(nerves in the upper back) supply movement and sensation to the trunk and abdomen.
Lumbar and Sacral nerves - CNS
(nerves in the lower back) supply movement and sensation to the legs, the bladder, bowel and sexual organs.
Somatic nervous system
◦The part of the peripheral nervous system that controls the movement of skeletal muscles or transmits somatosensory information to the central nervous system from the skin and sense organs
◦Spinal nerves and cranial nerves
autonomic nervous system
◦The portion of the peripheral nervous system that controls the body’s vegetative functions (smooth muscle, cardiac muscle and glands)
◦Sympathetic and parasympathetic nervous system
Spinal nerves - PNS (SNS)
◦From the vertebral column, fibers travel to muscles or from sensory receptors
◦Afferent axons (to CNS) and efferent axons (from CNS)
◦Dorsal root ganglion = neuron bundle along dorsal root
Cranial nerves - PNS (SNS)
◦12 pairs attached to ventral surface of brain
◦Sensory/motor function of head and neck
◦Vagus nerve (X) regulates thoracic and abdominal cavities
Sympathetic nervous system - PNS (ANS)
◦activation associated with energy expenditure and mobilization (e.g., increased blood pressure, heart rate, epinephrine release)
◦Via preganglionic neurons in spinal nerves at thoracic and lumbar regions (thoracolumbar) of the CNS to postganglionic neurons that stimulate target tissue = sympathetic ganglion chain
Parasympathetic nervous system - PNS (ANS)
◦processes associated with conserving and restoring energy (e.g. salivation, blood flow to gastrointestinal tract, digestion)
◦Preganglionic axons stem from cranial and sacral region (craniosacral) and connect to postganglionic cells in intermediate vicinity of target cells.
What protects the brain? (3)
1.Blood Brain Barrier
2.Meninges
3.Cerebral Spinal Fluid (CSF)
meninges
Layers of connective tissues that protect the CNS
Name 3 layers that encase the CNS and protect the brain and spinal cord
◦Dura mater: tough, flexible
◦Arachnoid membrane: soft, spongy
◦Pia mater: thin, delicate
Parts of the ventricular system
- Lateral ventricles
- Third ventricle
- Fourth ventricle
- Interventricular foramen
- Cerebral aqueduct
- Choroid plexus
Lateral ventricle
largest ventricle located in the center of the telencephalon
Third ventricle
located in the center of the diencephalon
Fourth ventricle
located between cerebellum and dorsal pons in the center of the metencephalon
Intraventricular foramen
connects the lateral and the third ventricle; located anterior to massa intermedia
Cerebral aqueduct
a narrow tube connecting the third and fourth ventricle
Choroid plexus
special tissue that manufacture CSF and protrudes into all 4 ventricles (ependymal cells)
CSF circulation steps:
- CSF is produced by the choroid plexus of each ventricle
- CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal chord.
- CSF flows through the subarachnoid space
- CSF is absorbed into the dural venous sinuses via the arachnoid villi.
Why is CSF important?
- Provides a protective buoyancy for the brain which effectively makes the weight of the brain 1/30th of its actual weight.
- Cushions the brain against mechanical shock (think TBI)
- Contributes to the chemical environment of the central nervous system
The one-way flow of CSF from the ventricular system, around the spinal cord, into the subarachnoid space and into the venous sinuses, where it is reabsorbed, is a way in which potentially harmful metabolites are removed.
CSF issues: (2)
◦Hydrocephalus
◦Normal Pressure Hydrocephalus
