i want 25 multiple choice questions with tehir model answer below each question about the various aspects of :Objective 1.State & describe the nerve endings in epithelium ,connective tissue & muscular tissue.
2.Structure of blood brain barrier (BBB)Nerve Endings: Nerve endings are either
A. Receptors that receive external or internal
stimuli and convert.
They are classified into ;
•Exteroceptors which receive external stimuli.
•Proprioceptors which receive stimuli from muscle.
•Interceptors which receive internal stimuli.
B. Effectors that bring efferent nerve impulses to
effectors (muscle or gland).Nerve Endings in EpitheliumA- Receptors:
are exteroceptors
1. Free nerve endings
2. Merkel endings
3. Peritrichial nerve endings
4. Neuroepithelim endings1.Free nerve endings :
• They are mechanoreceptors for pain
,temperature ,touch, pressure, itching.
•In epidermis of skin and cornea of eye.
•nonecapsulated .Myelinated nerve loses its myelin
below the basement membrane and pass in
between the epithelial cells.
2. Merkel endings:
• They are mechanoreceptors (prolonged touch or pressure
on the skin).
•They are present in the epidermis of the skin of palm and
sole.
•The nerve loses its myelin sheath and form a disc like
expansion under Merkel cell near the base of epidermis..3.Peritrichial nerve endings:
• Free nerve endings incorporated
in the hair follicles that respond to
touch and movement of hair
(mechanoreceptors).
4.Neuroepithelim endings:
•
•
•
Taste buds in tongue for taste.
Organ of Corti in ear for hearing.
Macula utriculi, macula sacculi and
cristae ampullaris for equilibrium
♦Retina of eye.
♦ Olfactory epithelium of noseB- Effectors:
These are autonomic nerve
endings supplying glandular
epithelium as lacrimal and
salivary glands. The
umyelinated nerve fibres form
networks just outside the basal
lamina of the epithelium. From
there, branches penetrate the
lamina and end between the
bases of the glandular cells.Nerve Endings in Connective Tissue
All are receptors;
1 -Free nerve endings:
2-Meissner's corpuscle:
3-Krause's end bulb:
4-Ruffini's end organ:
5-Pacinian corpuscle:
6-Golgi tendon organ
(Tendon spindle):Nerve Endings in Connective Tissue :
All are receptors;
1 - Free nerve endings:
•
Similar to those in epithelium.
•
Present in the dermis of skin and stroma of cornea.
2- Meissner's corpuscle:
• Encapsulated, pear shaped.
•
In dermal papillae of skin that is especially sensitive as tips of fingers.
• The axon enters the corpuscle after losing its myelin and spirals up
between the cell layers until it ends at the upper pole of corpuscle.
•
It is a mechanorector (touch).
3-Krause's end bulb:
• Encapsulated, spherical bodies.
• Deep in the dermis of skin.
• The axon enters the corpuscle after losing
its myelin and branches repeatedly inside.
•
It is a mechanorector (touch).Nerve Endings in Connective Tissue
4-Ruffini's end organ:
• Encapsulated, fusiform bodies.
• Deep in dermis of skin especially in sole.
• The axon enters the capsule after losing myelin sheath &
branches between parallel collagen fibres inside.
• It is a mechanoreceptor that responds to tension forces.
5-Golgi tendon organ (Tendon spindle):
• Proprioceptor nerve ending in tendons near
the insertion sites of muscle fibres.
• It is formed of connective tissue sheath surrounding large
bundles of collagen fibres that are continuous with the collagen fibres of tendon.
• Sensory nerve penetrates the capsule to end around the collagen bundles.
• Collects information about difference
in
tension among
tendons and relays data to CNS to help in coordination of muscular contraction.Nerve Endings in Connective Tissue
Pacinian corpuscle:
•Encapsulated, large ovoid up to 1 mm in length.
•In dermis and hypodermis of skin, periosteum of bone, joint
capsule and in connective tissue of some organs as pancreas.
•It has a thin connective tissue capsule enclosing 20-60
concentric lamellae
consisting of very thin flat cells (probably modified Schwann cells)
separated by narrow spaces filled with gel like material. Towards the
centre, the lamellae become closely packed.
•The myelinated nerve fibre enters the corpuscle at one pole. Its
Schwann cell sheath becomes continuous with the capsule while
the myelin sheath ends inside the corpuscle. The naked nerve fibre
runs parallel to the longitudinal axis and ends in a small expansion.
•It is a mechanoreceptor for pressure, vibration and
tension. It is one of the proprioceptors.Nerve Endings in Muscular Tissue
A- Receptors:
Muscle spindles:
• Proprioceptors within the skeletal muscle which are responsible for
regulation of the muscle tone through stretch reflex, participate in control
of body posture and the coordinate action of opposing muscles.
•Site: More numerous in muscle involved in fine movements as intrinsic
muscle of hand and in antigravity muscles.
•They lie parallel to muscle fibres.
• Shape: fusiform
• Size: up to 6 mm long but less than 1 mm in diameter.•Structure: Capsule surrounding
lymph filled space that contains intrafusal
fibres and nerve fibres.
I ntrafusal fibres: much smaller than
skeletal muscle fibres and they have central
non striated area containing the nuclei.
They are of 2 types:
Nuclear bag type: the central nuclear
area is dilated.
Nuclear chain type: no dilatation and
the nuclei are in the form of chain.Nerve Endings in Muscular Tissue Afferent nerves: I-Annulospiral endings: myelinated large nerve fibres that envelope the non striated central portion of intrafusal muscle fibres. II-Flower-spray endings: myelinated small nerve fibres that are located on striated peripheral portion of intrafusal muscle fibres. Efferent nerves: Gamma motor nerve fibres innervate striated portion of intrafusal muscle fibres. NB: Alpha motor nerve fibres innervate the extrafusal muscle fibres.Blood Brain Barrier1-Blood brain barrier:
Definition: It is the barrier
between the blood and the nerve
cells. Structure: It is formed of;
• Tight junction between non
fenestrated endothelium lining
capillaries.
• Thick continuous basement
membrane (Basal lamina).
• End feet of astrocytes firmly
applied on capillaries.Function:
• Prevents harmful materials from reaching the
nerve cells.
• Allows nutrients and precursors of
neurotransmitters to pass by facilitated diffusion and
active transport .Blood CSF barrier2- Blood CSF harrier-
Definition: it is the barrier that separates blood from CSF.
Structure: it is formed of;
• Endothelium of choroidal capillary.
• Basement membrane of the choroidal capillary.
• Basement membrane of ependymal cells forming the
choroid plexus.
• Tight junctions between ependymal cells forming the
choroid plexus,Function:
• Protection.
• Selection of substances to pass trom
blood to CSF.
• Maintenance and constancy of CSF3- Arachnoid barrier: Definition: It is the barrier between extracerebral capillaries and subarachnoid space Structure: it is the arachnoid barrier layer formed of cells joined by tight junctions and desmosomes. Function: block substances leaving extracerebral capillaries from reaching subarachnoid space, brain tissue and ventricles