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The Central Nervous System
CNS
– CNS: brain and spinal cord– Necessary for the maintenance of
homeostasis– Contains 1011 neurons– Contains 1014 synapses– Responsible for everything we perceive, do,
feel, and think
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Cerebrum
• Five paired lobes within two hemispheres
• Gray matter in cortex and in deeper cerebral nuclei
• White matter inside
• Higher functions are performed by the brain
Brain matter
• What is gray and white matter?
• Gray matter: neurons and unmyelinated axons
• White matter: myelinated axons
Protection and Coverings
• Cranial bones• Meninges - 3 layers:
- Dura mater, Arachnoid, and pia mater
- Between dura mater and arachnoid: subdural space- In between arachnoid and pia mater, in subarachnoid
space: cerebro-spinal fluid (CSF)
Meninges
Meninges
Meningitis
CSF
• Cushion the brain• Provide a constant IF environment• About 150 ml• Produced by the ependymal cells of the choroid
plexus, in the ventricle• Resorbed by the arachnoid granulations• Continuously produced and continuously
resorbed• Composition slightly different from plasma
Cerebrospinal fluid circulation
CSF circulation
Hydrocephalus
• A blockage of CSF circulation will trigger an accumulation of CSF in the ventricle
• This will result in hydrocephalus
Hydrocephalus
Blood supply
– CNS comprises 2% of body weight (3–4 pounds)
• Receives 15% of blood supply
– High metabolic rate• Brain uses 20% of oxygen consumed by body
at rest• Brain uses 50% of glucose consumed by body
at rest
– Depends on blood flow for energy
Energy supplies
– Depends on aerobic glycolysis– Requires glucose and oxygen– No glycogen stores– Fatty acids not used for energy – Ketones used during extreme conditions
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Brain structure
Cerebrum
• Two hemispheres
• Surface have gyri, grooves(sulci) and fissures
• Two fissures: longitudinal (falx cerebri and cerebelli) and transverse (tentorium cerebelli)
• Corpus callosum
Cerebrum
• Cerebral cortex
- Lobes: 1 frontal, 1 parietal, 1 occipital, and 2 temporal and insula – surface is gray matter - Basal nuclei (or ganglia)- gray matter deep
inside white matter.
Frontal lobe
• Voluntary motor control
• Personality• Concentration,
planning, decision making
• Verbal communication
Frontal lobe : Motor area
Language
• Broca’s aphasia: due to damage in the Broca’s area of the brain. Speech slow and poorly articulated
• Wenicke’s aphasia: due to damages to Wernicke’s area produces a rapid speech without meaning. Comprehension destroyed
Speech areas
Parietal lobes
• Sensory interpretations
• Understanding speech
• Formulating words to express thoughts and emotions
• Interpretations of textures and shapes
Sensory areas
“Small brain”
Temporal lobes
• Interpretation of auditory sensations
• Memory of auditory and visual experiences
Occipital lobe
• Perception of vision• Vision recognition• Focusing and eye
movement
Memory
• Short and long term memory• Several regions of the brain involved,
especially temporal lobe, hyppocampus• Short long term memory: medial
temporal lobe• Long term memory independent of
temporal lobe• Memory acquisition possible due to
synapse changes
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Basal Nuclei
• Mass of neurons located deep into the white matter
• Help control of voluntary movement
Basal Nuclei
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Diencephalon
Diencephalon
• Thalamus:4/5 of diencephalon
• Below lateral ventricles
• Relay center through which sensory informations (except smell) pass, on the way to the cortex
• Many nuclei
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Diencephalon: Hypothalamus and pituitary gland
• Below thalamus
• Neural centers for many functions:
- hunger, thirst, body temperature regulation
- controls pituitary gland
- contribute to sleep regulation, emotions (fear, anger, pain, pleasure..), sexual arousal
Hypothalamus
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Midbrain
• Between diencephalon and pons• Several nuclei: - corpora quadrigemina: visual and auditory
reflexes - red nucleus: motor coordination - nigrostriatal system (from substancia nigra-
basal ganglia) motor coordination (involved in Parkinson’s disease)
- cerebral peduncles: ascending and descending fiber tracts
Midbrain
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Pons
• Between midbrain and medulla oblongata
• Several nuclei associated with cranial nerves (V, VI, VII, and VIII)
• Respiratory centers: apneustic and pneumotaxic centers
• Communicates with cerebellum and medulla oblongata, and midbrain
Pons
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Medulla oblongata
• Between pons and spinal cors
• Numerous nuclei controlling cranial nerves (VIII,IX,X,XI, and XII), and vital functions: vasomotor, cardiac, respiratory, sneezing, swallowing centers
• Passageway for sensory and motor fibers
• Fibers “decussate” or cross over
Medulla oblongata
Cerebral lateralization
• The cerebral cortex controls movement of the contralateral side
• Sensations project to the contralateral side of the parietal lobes
• The two hemispheres communicate through the corpus callosum
• Left side: language and analysis
• Right side: visual spatial tasks
Medulla oblongata
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Limbic system
• Emotion & motivation• Mesh of neurons
around the brain• Connect to
hypothalamus• Involved in control of:
- aggression, fear, feeding, sex and goal-directed behavior
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Reticular formation
• Complex network of nuclei and nerve fibers in medula, pons, midbrain, diencephalon
• Reticular Activating System (RAS): maintain a state of alert consciousness
The Brain• BRAIN MATTER AND CEREBROSPINAL FLUID• CEREBRUM• a- Cerebral hemispheres• a1- Lobes• a2- Basal ganglia (nuclei)• b- Brain stem• b1-Diencephalon• b1-1- Thalamus• b1-2- Hypothalamus• b2- Midbrain• b3- Pons• b4- Medulla oblongata• c- Limbic system• d- Reticular formation• CEREBELLUM
Cerebellum
• “small brain”
• Fibers from cerebellum red nucleus thalamus cerebral cortex
• Other tracts connect cerebellum to pons, midbrain, medulla
• Receives input from proprioreceptors (from muscles, tendon) coordinates movement, control equilibrium
Cerebellum
Readings
• Chp. 9, p. 216-236
• Not expected to be known: