Week 2 Flashcards
What are the two main types of Nervous systems?
Central Nervous System (CNS) and Peripheral Nervous System (PNS)
What does the Central Nervous System consist of?
Brain
Spinal cord
What does the Peripheral Nervous System consist of?
Somatic Nervous System (SNS)
Autonomic Nervous System (ANS)
What does the Somatic Nervous System (SNS) consist of?
Afferent nerves (incoming) Efferent nerves (outgoing)
What does the Autonomic Nervous System consist of?
Afferent nerves (incoming) Efferent nerves (outgoing) which have Parasympathetic (rest and digest) and Sympathetic (fight or flight)
Central Nervous System (CNS)
Brain and spinal cord
Encased in bone
Networks of interconnected neurons
Processing of information
Peripheral Nervous System (PNS)
Outside the skull and spine Nerves – bundles of separate neurons Transmission of information Connects the CNS with the rest of the body Somatic Nervous System (SNS) Voluntary Interaction with the environment Autonomic Nervous System (ANS) Involuntary Regulate the body
Somatic Nervous System (SNS)
Voluntary Interaction with the environment Afferent Incoming signals Sensory info into the CNS Exteroceptive sense organs Information to enable interaction with the world Efferent Outgoing signals Motor commands from the CNS Skeletal Muscle Facilitate bodies interaction with the world
Autonomic Nervous System (ANS)
Involuntary Regulate the body Afferent Incoming signals Sensory info into the CNS Interoceptive sense organs (viscera and blood vessels) Information about the body’s internal state Efferent Outgoing signals Motor commands from the CNS Smooth and cardiac muscle and glands Change the body’s internal state
ANS Efferents
Sympathetic
Fight or flight
Stimulate organs and release hormones to wind things up
Mobilise energy sources
Increase blood flow and respiration
Supress non-essentials
Parasympathetic
Rest and digest
Counteract sympathetic to wind things down
Stimulate digestion and restorative functions
Conserve energy
CNS / PNS Interface
Cranial Nerves
12 pairs
Connect directly to the brain
Some purely sensory, some purely motor, some both
Spinal Nerves
31 pairs
Connect to the spinal cord
All are both sensory and motor
Neurons
Main functional cells of the nervous system
Collect, integrate and transmit information
Glia
Glia support neurons
Numerous types and many function
Clusters of cells within the CNS and PNS
CNS - Nuclei
PNS – Ganglia
in grey matter
Clusters of axons within the CNS and PNS
CNS - Tracts
PNS – Nerves
in white matter
4 Main Types of Neuron
Unipolar neuron- Sensory neurons transfer information from receptor cells to higher nerve cells
Bipolar neuron- Connecting adjacent cells typically in sensory system (e.g. retina)
Multipolar neuron- Transfer information between cells usually long distance; can collect and integrate info from many cells
Multipolar interneuron- Local connections collect and integrate info from many cells
4 Main Types of Glia
Oligodendrocytes- Myelination in CNS
Schwann Cells- Myelination in PNS
Microglia- Immune function
Astrocytes- Numerous structural and functional support
The Spinal Cord
13-14 million neurons
Protected by the vertebral column (and meninges)
Doesn’t go full length of the spine
Loose bundle of nerves below L2 – Cauda Equina (horses tail)
Messages to and from the brain
Also simple processing – reflex arcs
The spinal cord cross section consists of?
Dorsal horn Dorsal root Dorsal root ganglion Ventral horn Ventral root Spinal nerve
The two main types of nerves to the spinal cord are?
Unipolar afferent neurons join the dorsal horn - both somatic (skeletal / sensory) and autonomic (internal organs) systems.
Multipolar efferent neurons have their cell bodies in the ventral root. Their axons project out to somatic and autonomic systems.
The development of the brain and the neural tube
neural plate border, neural plate and epidermis
convergence of the neural plate borders to create a neural fold
the formation of the epidermis, neural crest an neural tube
The sections of the brain
Forebrain
Midbrain
Hindbrain
Spinal cord
Five Divisions of The Brain
Forebrain -Telencephalon -Diencephalon Midbrain -Mesencephalon Hindbrain -Metencephalon -Myelencephalon
Brainstem
Connects forebrain to spinal cord
White matter outside with grey matter inside in discrete nuclei
3 major levels
Myelencephalon
Metencephalon
Mesencephalon
All head muscles supplied by cranial nerves from the brainstem
Myelencephalon
Medulla
Caudal brainstem – blends into spinal cord
Primarily axonal tracts
Pyramidal tracts – ‘decussation of the pyramids’
Head and neck movement
Vital functions
Portion of reticular formation (net-like formation) - arousal.
Mesencephalon
Midbrain -tectum and tegmentum Tectum superior and inferior colliculi Visual and auditory orienting of attention Multisensory integration
Tegmentum
Portion ventral to tectum
Periaqueductal grey matter
Substantia nigra
Mesencephalon- Parkinson’s Disease
Loss of dopamine neurons in SN Project to basal ganglia Important for movement control Tremor or shaking Muscle rigidity or stiffness Slowing of movement Stooped posture Balance problems.
Diencephalon
Forebrain
2 major parts
Thalamus
Hypothalamus
2 major endocrine glands
Pituitary gland
Pineal gland
Thalamus
Relay station – all sensory except smell relays through thalamus
Also receives many cortical projections
Integration of bottom-up inputs and top-down
Many separate nuclei
Lateral Geniculate Nucleus first synapse after the optic nerve leaves the eye
Medial Geniculate Nucleus Auditory relay
Ventro Posterior Nucleus Sensorimotor relay
Hypothalamus
Ventral part of diencephalon
Control centre for autonomic nervous system
Inputs from many brain and body systems
Outputs to brainstem (ANS) and pituitary gland (endocrine)
Homeostasis
Regulation of motivated behaviours – eating, sleeping, sexual
Telencephalon
Forebrain
Collection of subcortical nuclei
Cerebral cortex
Basal Ganglia
Control of movement
Learning and motivation
Striatum – caudate + putamen
Limbic System
Midline structures circling the thalamus
Regulation of motivated behaviours - The Four Fs
Affect/emotion
Amygdala – learned fear response; recognition of emotion in others
Hippocampus – long term memory
Cerebral Cortex
Layer of grey matter covering the cerebral hemispheres
Folded – Gyri (ridges) and Sulci (fissures)
2 Hemispheres connected by corpus collosum
4 lobes
Many regions or areas based on location (e.g. PFC), function (e.g. FEF), or cytoarchitecture (e.g. Brodmann areas)
28 billion neurons
>1 trillion synapses
>80% human brain mass
The four parts of the cerebral cortex
Frontal Lobe
Thinking, planning, executive functions, motor execution
Parietal Lobe
Somatosensory perception, spatial perception
Temporal Lobe
Auditory, language, long term memory, emotion
Occipital Lobe
Visual
Main Neuron Types
Pyramidal
Most common cortical neuron
Large bodies, multipolar, long axon goes down and inward through layers
Projection neurons – connect disparate brain regions or leave the brain (to spinal cord)
Stellate
small, star-shaped short axons; transmit info laterally
Local – interneurons
Layers of Neocortex
Most cortex neocortex – new
6 layered outer covering of the cerebral hemisphere
Each layer differs in the relative concentration of stellate and pyramidal cells, in the relative size and concentration of cell bodies
Layer I - axons and dendrites, few cell bodies
Layer II - densely packed stellate cells , a few pyramidal cells
Layer III - Loosely packed stellate cells; intermediate sized pyramidal cells
Layer IV is thick in sensory areas – Input
Layer V – mainly pyramidal cells with long axons - in motor areas - output
Layer VI - pyramidal cells of various sizes; loosely packed stellate cells
Protecting the Brain
Physical protection from mechanical injury Skull 3 Meninges (Dura Mater, Pia Mater, Arachnoid) – membranous coverings around the brain and spinal cord Cerebrospinal fluid (CSF) – supports and cushions
Chemical protection – maintaining chemical balance
The blood-brain barrier
Tightly packed cells along the blood vessel walls of the CNS prevent entry of many (large) molecules.
Good and bad (eg L-Dopa)
Physical protection of the brain - in order
Scalp Skull Dura Mater Arachnoid membrane Sinus Arachnoid membrane Sub-arachnoid space Artery Pia mater maninx Cortex
The ventricles
Lateral Third Cerebral aqueduct Fourth Central canal
Cerebrospinal Fluid
Produced by choroid plexuses in ventricles
Circulates subarachnoid space, ventricles and central canal
Excess drains into sinuses in the dura mater
If drainage is blocked - hydrocephalus
Commisurotomies / callosotomies
Antecedent: usually sever epilepsy
Procedure: callosotomy, anterior commissurotomy
Consequence: reduction of seizures
Behavioural consequence: very little
Experimental consequence: sensory information presented to one hemisphere is not available to guide behaviour in the other hemisphere
Split Brains
Visual information – left visual field to right hemisphere and right visual field to left hemisphere
Intact brain – information can cross between hemispheres via the corpus callosum
Callosotomy – lose communication
Left hemisphere ignorant of left visual field
Right hemisphere ignorant of right visual field
Left hemisphere ignorant of left visual field
Right hemisphere ignorant of right visual field
But – speech typically in left hemisphere
Split Brains- explain your behaviour
confabulation- subconsciously make reasons for what they say or do
