Nerve 2 (Anatomy) Flashcards
Describe the anatomy of the brain
- The brain can be divided into three portions known as the cerebrum, cerebellum, and brainstem.
- The cerebrum is about 83% of the brain’s volume and consists of a pair of half globes called the cerebral hemispheres.
- Each cerebral hemisphere is marked by thick folds called gyri which are separated by grooves called sulci.
- A deep median groove called the longitudinal fissure separates the two cerebral hemispheres.
- At the bottom of the longitudinal fissure the cerebral hemispheres are joined together by a thick bundle of nerve fibres called the corpus callosum.
- The cerebellum occupies the posterior cranial fossa inferior to the cerebrum, separated from it by the transverse cerebral fissure.
- The cerebellum constitutes about 10% of the brain’s volume but contains over 50% of its neurones.
- The brainstem is all of the brain except the cerebrum and cerebellum.
- The major components of the brainstem are the diencephalon, midbrain, pons, and medulla oblongata.
- The brainstem sits inferior to the cerebrum.
- The grey matter in the brain forms a surface layer over the cerebrum and cerebellum called the cortex, and deeper masses called nuclei.
- White matter lies deep to the cortical grey matter and is composed of bundles of axons which connect one part of the brain to another and to the spinal cord.
Describe the major lobes, gyri and sulci of the brain
Frontal lobe
- Involved in decision making, problem solving, deliberate movement, and emotions.
- Lies immediately behind the frontal bone, superior to the eyes.
- Extends caudally to the central sulcus.
Parietal lobe
- Involved in processing sensory information, body orientation, and attention.
- Forms the uppermost part of the brain and underlies the parietal bone.
- From the central sulcus it extends caudally to the parieto-occipital sulcus.
Occipital lobe
- Involved in visual processing and object recognition.
- At the rear of the head, caudal to the parieto-occipital sulcus and underlying the occipital bone.
Temporal lobe
- Involved in auditory processing, language comprehension, and speech.
- A lateral, horizontal lobe underlying the temporal bone.
- Separated from the frontal and parietal lobes above it by the lateral sulcus.
Insula
- Involved in taste, pain, visceral sensation, and cardiovascular homeostasis.
- Small mass of cortex under the lateral sulcus.
- Only made visible by retracting some of the overlying cerebrum.
Name the major components of the brain and relate specific areas to their function
Cerebrum
- Different lobes and functions
Diencephalon
- Consists of the thalamus, hypothalamus, and the pineal gland.
Thalamus
- Consists of at least 23 nuclei.
- Relays sensory information between brain regions.
- Serves in motor control by relaying signals from the cerebellum to the cerebrum and providing feedback loops between the cerebral cortex and the basal nuclei.
- Involved in the memory and emotional functions of the limbic system.
Hypothalamus
- Links the nervous system to the endocrine system via the pituitary gland.
- Controls body temperature, hunger, thirst, sleep, and circadian rhythms.
Pineal gland
- Produces melatonin which regulates sleep patterns in both circadian and seasonal cycles.
Cerebellum
- Important role in motor control.
- Contributes to coordination, precision, and accurate timing
- The two dominant neurones are purkinje cells and granule cells.
Midbrain (or mesencephalon)
- Associated with vision, hearing, motor control, circadian rhythm, alertness, and temperature regulation.
Pons
- Relays sensory information to cerebellum and thalamus.
- Involved in subconscious somatic and visceral motor centres.
Medulla oblongata
- Contains the cardiac, respiratory, vomiting, and vasomotor centres and therefore deals with the autonomic functions of breathing, heart rate, and blood pressure.
Corpus callosum
- A large white matter tract that connects the two cerebral hemispheres.
- Forms the floor of the longitudinal fissure and part of the roof of the lateral ventricles.
- Has four main parts that are individual nerve tracts which connect different parts of the hemispheres.
- The four nerve tracts are the rostrum, the genu, the trunk/body, and the splenium. (Rostrally to caudally).
Circle of Willis
- Is the arterial supply of the brain.
- Internal carotid and vertebral arteries.
Describe the three meningeal layers of the brain
The meninges refer to the membranous coverings of the brain and spinal cord. The meninges provide a supportive framework for the cerebral and cranial vasculature, and act with the cerebrospinal fluid to protect the CNS from mechanical damage.
Dura mater
- Layer of dense connective tissue continuous with the periosteum of the the skull.
Arachnoid mater
- Transparent membrane over the brain surface, underlying the dura mater.
- Has a layer in contact with the dura mater and a system of trabeculae connecting the layer with the pia mater.
- The cavity between the trabeculae is called the subarachnoid space which is filled with cerebrospinal fluid and contains the largest blood vessels of the cerebral surface.
Pia mater
- Loose connective tissue containing many blood vessels and covered by squamous cells.
- Very thin and tightly adhered to the surface of the brain and spinal cord.
- The only covering to follow the contours of the brain (gyri and fissures).
Describe the structure of the choroid plexus and its role in producing cerebrospinal fluid
- There are four choroid plexuses in the brain, one in each of the ventricles.
- Each choroid plexus is a spongy mass of blood capillaries covered by modified ependymal cells.
- The ependymal cells produce the cerebrospinal fluid.
Describe the anatomy of the spinal cord
- Consists of 31 segments, each of which give rise to a pair of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
- Begins at the base of the medulla oblongata (arises from the foramen magnum) and travels inferiorly within the vertebral canal, surrounded by the spinal meninges containing cerebrospinal fluid.
- At the L2 vertebral level the spinal cord tapers off, forming the conus medullaris.
- The spinal nerves arising from the end of the spinal cord bundle together to form the cauda equina.
- The spinal nerves are mixed nerves originating from the spinal cord to form the peripheral nervous system.
- Each spinal nerve begins as and anterior/ventral (motor) and a posterior/dorsal (sensory) nerve root.
- These nerve roots arise from the spinal cord and unite at the intervertebral foramina, forming a single spinal nerve.
- The single spinal nerve leaves the vertebral canal via the intervertebral foramina and divides into the posterior rami and the anterior rami.
- The posterior rami supplies nerve fibres to the synovial joints of the vertebral column, deep muscles of the back, and the overlying skin.
- The anterior rami supplies nerve fibres to much of the remaining areas of the body, both motor and sensory.
What is a lumbar puncture
- A diagnostic test for bacterial meningitis, viral encephalitis, and idiopathic intracranial hypertension.
- Usually performed between L3/L4 in adults and L4/L5 in children.
- If performed wrong can cause paralysis and death.
What is the purpose of cerebrospinal fluid
Buoyancy, protection, prevention of brain ischemia, homeostasis, and clearing waste.
What is the term given for abnormal accumulation of cerebrospinal fluid on the brain
Hydrocephalus
What is the term given for lack of oxygen to the brain
Brain ischemia
