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Nervous System II: BrainLecture 13

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Brain

Major parts of the brain– Brainstem– Cerebellum– Diencephalon– Cerebrum

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Brainstem

• Connects spinal cord to brain• Parts

– Medulla oblongata– Pons– Mesencephalon

Fig. 15.1

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Brainstem• Medulla oblongata or medulla

– Regulates: Heart rate, blood vessel diameter, respiration, swallowing, vomiting, hiccupping, coughing, and sneezing

• Pons– Sleep and respiratory center

• Mesencephalon– Integral part of auditory

pathways in CNS

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Cerebellum• Involved in control of:

balance, posture, locomotion, and fine motor coordination producing smooth flowing movements

Fig. 15.22

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Diencephalon• Components

– Thalamus, Epithalamus, Hypothalamus

Fig. 15.15

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Diencephalon• Thalamus

– Largest part of diencephalon

– Most sensory input projects to here

– Influences mood and actions as fear or rage

• Epithalamus– Pineal gland may

influence sleep-wake cycle

• Hypothalamus– Functions

• ANS control• Endocrine control• Muscle control• Temperature

regulation• Regulation of food

and water intake• Emotions• Regulation of sleep-

wake cycle

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Cerebrum• Largest portion of brain• Hemispheres

– Right – Left– Lobes: frontal, parietal,

occipital, temporal, insula• Gyrus• Sulcus

Fig. 15.10

Fig. 15.1

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Meninges• Connective tissue

membranes– Dura mater:

Superficial– Arachnoid mater– Pia mater:

Bound tightly to brain

– Spaces • Subdural:

Serous fluid• Subarachnoid:

Cerebrospinal fluid (CSF)

Fig. 15.4

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Ventricles

• Ventricles: Lateral ventricles (2), third ventricle, fourth ventricle

• Choroid plexuses produce CSF which fills ventricles and other parts of brain and spinal cord

Fig. 15.6

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Cerebrospinal Fluid (CSF)

• Similar to serum with most of proteins removed

• Bathes brain and spinal cord• Provides a protective cushion around CNS• Provides some nutrients to CNS tissues• Produced by ependymal cells in the

ventricles of the brain

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Brain Blood Supply• Brain

– Requires tremendous amount of blood– Receives 15-20% of blood pumped by heart– Interruption can cause unconsciousness and

irreversible brain damage– High metabolic rate and dependence on

constant supply of oxygen and glucose– Receives blood through arteries

• Internal carotid arteries (carotid canal) and vertebral arteries (foramen magnum)

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Review Question

The primary link between the nervous system and the endocrine system (consists of glands that secrete hormones) is the

(a) Hypothalamus(b) Pons(c) Medulla oblongata(d) Cerebellum(e) Midbrain

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Points to Remember• Major parts of brain are: brain stem, cerebellum,

diencephalon and cerebrum.• Injury to medulla oblongata often fatal since it

contains vital parts for control of breathing, heart rate and blood pressure.

• Cerebellum provides important control of skeletal muscles for coordination of movement and posture.

• Diencephalon functions in several emotions and control of sleep-wake cycle.

• Cerebrum is largest part of brain with functions in emotions, higher level thinking, interpretation of sensory data and muscular control.

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Questions?