The Central Nervous System

Outline of diencephalon Cerebral hemisphere Outline of diencephalon Midbrain Cerebellum Pons Medulla oblongata Spinal cord (a) Week 13 Figure 7.12

Features of the Cerebrum Anterior Surface markings Gyri = ridges Sulci = shallow grooves Fissures = deep grooves Lobes Frontal Parietal Temporal Occipital Longitudinal fissure Left cerebral hemisphere Right cerebral hemisphere Longitudinal fissure separates the cerebrum into left and right cerebral hemispheres Posterior

Precentral Central gyrus sulcus Postcentral gyrus Frontal lobe Parietal lobe Occipital lobe Temporal lobe Cerebellum Central sulcus –Separates frontal from parietal lobes Precentral gyrus – anterior to central sulcus Also known as the primary motor cortex – responsible for conscious movement of skeletal muscles Postcentral gyrus – posterior to central sulcus Also known as the somatic sensory area – impulses from the body’s sensory receptors are interpreted in this area Lateral sulcus – divides the temporal from frontal and parietal lobes Occipital lobe –visual area of the brain; interprets impulses from optic nerve Temporal lobe – contains the auditory area and olfactory area Fissure Gyrus Cortex (gray matter) Sulcus White matter (a) Figure 7.13

The Principal Parts of the Adult Brain Cerebrum Diencephalon Cerebellum Brain stem (b) Adult Brain Figure 7.12

Cerebral Cortex Thin superficial layer of gray matter Deeper white matter composed of fiber tracts carrying impulses to or from cortex Corpus callosum- connects cerebral hemispheres

Diencephalon Enclosed by cerebral hemispheres 4/23/2017 Enclosed by cerebral hemispheres Major structures of diencephalon: Thalamus Hypothalamus Epithalamus 11

4/23/2017 Thalamus Relay station for sensory impulses passing up to sensory cortex Encloses the 3rd ventricle

Hypothalamus Below thalamus Floor of diencephalon 4/23/2017 Hypothalamus Below thalamus Floor of diencephalon Pituitary hangs from hypothalamus Important autonomic nervous center for: Body temperature Metabolism Water balance

Epithalamus Forms roof of 3rd ventricle 4/23/2017 Epithalamus Forms roof of 3rd ventricle Pineal body- part of endocrine system Choroid plexus – capillary beds which form CSF

Thalamus Epithalamus Hypothalamus Pituitary Gland

4/23/2017 The Brain Stem Midbrain Pons Medulla Oblongata

The Midbrain Superior portion of brainstem 4/23/2017 The Midbrain Superior portion of brainstem Cerebral aqueduct passes through to connect 3rd ventricle above and 4th ventricle below Anteriorly composed of tracts called cerebral peduncles that Convey ascending & descending impulses Dorsally placed are corpora quadrigemina that are Reflex centers for hearing, vision

Cerebral Aqueduct Coropora Quadrigemina Cerebral Peduncles

The Pons Rounded structure just below midbrain 4/23/2017 The Pons Rounded structure just below midbrain Mostly fiber tracts that bridge areas of brain Contains nuclei involved in the control of breathing Pons 11

Medulla Oblongata Inferior portion of brain stem 4/23/2017 Medulla Oblongata Inferior portion of brain stem Many important fiber tracts Contains nuclei that regulate vital visceral activities Heart rate Blood pressure Breathing Swallowing, etc. Medulla Oblongata

Cerebellum Functions: Precise timing for skeletal muscle activity 4/23/2017 Cerebellum Functions: Precise timing for skeletal muscle activity Controls balance & equilibrium 11

Meninges Functions: Three layers Cover and protect the CNS Contain cerebrospinal fluid (CSF) Form partitions in the skull Three layers Dura mater Arachnoid mater Pia mater

Skin of scalp Periosteum Bone of skull Outer Dura mater Inner Superior sagittal sinus Arachnoid mater Pia mater Subdural space Subarachnoid space Figure 7.16

Meninges Dura Mater (Strongest, Outer layer) Two layers (fibrous CT); separate to form dural sinuses Dural septa – inward folds of dura mater Falx cerebri—in longitudinal fissure Falx cerebelli— separates cerebellum in half Tentorium cerebelli—horizontal; separates cerebellum and cerebrum

Falx cerebri Crista galli Of ethmoid bone Tentorium cerebelli Falx cerebelli (a) Dural septa

Meninges Arachnoid Mater- Middle layer Weblike Contains CSF & blood vessels Arachnoid villi extend into dural sinus; allow CSF reabsorption Pia Mater -Innermost layer Delicate vascularized CT that clings tightly to the brain

Ventricles of the Brain Connected to one another and to central canal of spinal cord Two C-shaped lateral ventricles in the cerebral hemispheres Third ventricle in diencephalon Fourth ventricle is dorsal to pons

Lateral ventricle Interventricular foramen Lateral aperture Third ventricle Lateral ventricles to third ventricle, through cerebral aqueduct into fourth ventricle. Some fluid in fourth ventricle passes down central canal of spinal cord, but most circulates into the subarachnoid space through openings in wall of fourth ventricle CSF forms and drains at a constant rate Any significant changes in CSF may be a sign of an infection Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view (b) Left lateral view Figure 7.17