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Anatomy of the Central Nervous System

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1 Anatomy of the Central Nervous System


3 Divisions of the Mammalian Nervous System
Central Nervous System = the brain and the spinal cord Peripheral Nervous System = the nerves outside the brain and spinal cord Two Divisions of the PNS Somatic Nervous System - the nerves that convey messages from the sense organs to and from the CNS Autonomic Nervous System - a set of neurons that control the heart, the intestines, and other organs

4 Nervous System PNS CNS SNS ANS Brain Spinal Cord
sympathetic parasympathetic



7 The Nervous System The Spinal Cord-part of the CNS found within the spinal column The spinal cord communicates with the sense organs and muscles below the level of the head Bell-Magendie Law-the entering dorsal roots carry sensory information …and the exiting ventral roots carry motor information to the muscles and glands Dorsal Root Ganglia - are clusters of neurons outside the spinal cord

8 Figure 4.3  Diagram of a cross section through the spinal cord The dorsal root on each side conveys sensory information to the spinal cord; the ventral root conveys motor commands to the muscles.

9 Autonomic Nervous System
Sympathetic - prepares the body for activity Increased breathing, and heart rate, decreased digestive activity Form chain of ganglia just outside spinal cord Short preganglionic axons release norepinephrine Long postganglionic axons release norepinephrine Parasympathetic - facilitates vegetative, non-emergency responses by the body’s organs Increase digestive activity, activities opposing sympathetic system Consists of cranial nerves and nerves from sacral spinal cord Long preganglionic axons extend from the spinal cord to parasympathetic ganglia close to each internal organ; release norepinephrine Shorter postganglionic fibers then extend from the parasympathetic ganglia in the organs; release acetylcholine

10 The Mammalian Brain There are 4 main parts to the brain:
1. Hindbrain (cerebellum + medulla oblongata) 2. Midbrain 3. Diencephalon ( thalamus + hypothalamus) 4. Forebrain (cerebral hemispheres)

11 The Brain The Hindbrain ( Posterior part of brain )
Medulla Oblongata - controls vital reflexes like breathing, heart beat Blood pressure (all via sympathetic and parasympathetic n.s.) Cerebellum – controls movement, shifts of attention, balance and coordination. Works by comparing intended with actual movement.

12 Medulla oblongata Para-sympathetic slows down Sympathetic speeds up Sino Atrial Node (SAN)

13 The Brain The Midbrain - middle of the brain
Connects fore and hind brains. Mainly responsible for movements such as head and eyes focussing on an object.


15 The diencephalon Thalamus Centre of forebrain
Relay Station for sensory information (‘switchboard’) Hypothalamus Regulates homeostasis, sexual behavior, fighting, feeding Pituitary Gland Endocrine gland attached to the base of the hypothalamus (ADH, GH, FSH, TSH)

16 Cerebrum (left and right cerebral hemispheres)
The Brain The Forebrain - most anterior and most prominent part of the mammalian brain, comprising the… Cerebrum (left and right cerebral hemispheres)

17 Figure 4.12 A sagittal section through the human brain

18 Left and Right hemispheres are linked by the CORPUS CALLOSUM.
The Cerebrum The cerebral hemispheres contain 109 nerve cells in a layer only 3mm thick. Left and Right hemispheres are linked by the CORPUS CALLOSUM. Each hemisphere has 4 LOBES: i) Frontal ii) Parietal iii) Temporal iv) Occipital

19 Frontal Lobe The Frontal Lobe-extends from the central sulcus (groove) to the anterior limit of the brain Contains Primary Motor Cortex – responsible for fine movements Contributes to shifting attention, planning of action, delayed response tasks as examples

20 Parietal Lobe The Parietal Lobe - between occipital lobe and the central sulcus Contains the primary somato-sensory cortex – i.e. receiving touch sensation, muscle-stretch information and joint position information Also, 3-D processing (visualisations, face recognition etc)

21 Temporal Lobe The Temporal Lobe - lateral portion of each hemisphere, near the temples Contains targets for hearing, essential for understanding spoken language (Wernicke’s Area), complex visual processes, emotional and motivational behaviors

22 Occipital Lobe The Occipital Lobe - posterior end of cortex
Contains primary visual cortex

23 Figure 4.20  Some major subdivisions of the human cerebral cortex The four lobes: occipital, parietal, temporal, and frontal.

24 Which part of the brain contains:
The cerebrum? Forebrain The cerebellum? Hindbrain The medulla oblongata? Pituitary gland? Diencephalon.

25 Which lobe of the cerebrum deals with:
a) memory b) vision c) language d) hearing e) spatial awareness

26 Essay for next week: a) Outline the functions of the cerebrum in the human brain. b) Describe the changes that occur in the cerebrum of a person with Alzheimer’s disease and discuss the possible causes of the disease. Try a web search eg or





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