Neuroanatomy introduction Flashcards
Role of the Nervous System
- Detect changes in external and internal environment
- —-Receive sensory input
- Relay information and analyse it
- Initiate appropriate responses
What are neurons and what is their function?
- Most basic functional unit of nervous system
- Convey information via electrical signals
- Receive, Integrate, Transmit
- Afferent/ Sensory neurons
- —-Carry information from receptors to the CNS
- Efferent/Motor neurons
- —-Carry information from CNS to peripheral effectors
- Interneurons
- —-Link afferents to efferents within CNS
Subdivisions of the Nervous System
Central (brain and spinal cord) + Peripheral
Peripheral = Somatic (controls external actions) Autonomic (controls internal activities)
Autonomic = Sympathetic (arousing) and Parasympathetic (calming)
Sub-divisions of the CNS
- Cerebrum (forebrain)
- Consists of two parts:
- —- Outer brain (telencephalon)/Cerebral hemisphere
- —- Inner brain (diencephalon)
- Brainstem (Midbrain, pons, medulla oblongata)
- Cerebellum
- Spinal cord
Neural tube
This tube develops three swellings (A, B, C) and begins to form a bend at the rostral end
Caudal end of tube develops to spinal cord
Rostral end of tube develops into brain
A: Forebrain - Prosencephalon
B: Midbrain - Mesencephalon
C: Hindbrain - Rhombencephalon
2nd stage of the CNS development
Three swellings become five: Ai, Aii, B, Ci and Cii
Ai, Telencephalon; Aii, Diencephalon
B, Mesencephalon
Ci, Metencephalon; Cii, Myelencephalon
Development of mature brain from neural tube
Prosencephalon (A)
= front brain
- — 2 structures =
Telencephalon (Ai)
= far away brain which becomes the cerebral hemispheres.
and
Diencephalon (Aii)
= across brain which becomes the diencephalon (thalamus and hypothalamus)
Development of mature brain from neural tube
Primary vesicle = Mesencephalon (B)
= middle brain
- Mesencephalon (B)
= middle brain
— Mesencephalon in the secondary brain vesicles and the Midbrain in the Mature brain.
Development of mature brain from neural tube
Primary Vesicle: Rhombencephalon (C)
= rhomboid brain
- Secondary brain vesicles = 2 x structures
—–a. Metencephalon (Ci)
= behind brain which becomes the pons and cerebellum
and
—–b. Myelencephalon (Cii)
= marrow/cord brain which becomes the medulla oblongata.
Features of an adult brain
Series of gyri and sulci
White matter
- Axons
- Tracts
Grey matter
- Cell bodies
- Nuclei
- Point of synapse
Lobes of the Brain
- Frontal Lobe
- Parietal Lobe
- Temporal Lobe
- Occipital Lobe
What separates the 2 hemispheres of the brain?
Great Longitudinal fissure
What links the 2 hemispheres together?
Corpus Callosum
Sulci and Gyri function
Surface of cerebral hemispheres (i.e cerebral cortex) are heavily folded to increase surface area
Grey Matter and location
Neuronal cell bodies and located mostly on the outside part of the brain. Some e.g. basal ganglia located in the centre.
White matter
Nerve Axons
Spinal cord and Spinal nerves
33 Vertebrae (bones)
31 spinal cord segments 8 Cervical (C1-C8) 12 Thoracic (T1-T12) 5 Lumbar (L1-L5) 5 Sacral (S1-S5) 1 Coccygeal (Co1)
Each segment gives rise to
1 pair segmental spinal nerves
= 31 Pairs of spinal nerves (PNS)
Reason for the Cauda Equina
Growth of nerves stops way before the growth of bones. Nerves closer to the end of the column travel down the column before they can exit out near their respective vertebra.
Arrangement of the spinal nerve coming out of the column: Dorsal and Ventral?
Made of ventral and dorsal rootlets initially
Ventral rootlets > form a ventral root
Dorsal Rootlets > combine to form dorsal root first > then dorsal root ganglion (sensory neurones have the cell body ~halfway down the axon = the ganglion is where the cell bodies amass to create the swelling)
Dorsal + Ventral Roots > combine to form spinal nerve = motor and sensory neurones.
Peripheral Nervous System- 2 types of fibers and functions?
Sensory (Afferent) Fibers
Sends info TO the CNS
Motor (Efferent) Fibers
Sends info AWAY FROM the CNS
